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products/Sources/formale Sprachen/JAVA/Openjdk/src/java.base/share/classes/java/lang/ (Sun/Oracle ^©) Datei vom 13.11.2022 mit Größe 178 kB

Quelle String.java

Sprache: JAVA

/*
* Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

package java.lang;

import java.io.ObjectStreamField;
import java.io.UnsupportedEncodingException;
import java.lang.annotation.Native;
import java.lang.invoke.MethodHandles;
import java.lang.constant.Constable;
import java.lang.constant.ConstantDesc;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Formatter;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.Optional;
import java.util.Spliterator;
import java.util.function.Function;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import jdk.internal.util.Preconditions;
import jdk.internal.vm.annotation.ForceInline;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import jdk.internal.vm.annotation.Stable;
import sun.nio.cs.ArrayDecoder;
import sun.nio.cs.ArrayEncoder;

import sun.nio.cs.ISO_8859_1;
import sun.nio.cs.US_ASCII;
import sun.nio.cs.UTF_8;

/**
* The {@code String} class represents character strings. All
* string literals in Java programs, such as {@code "abc"}, are
* implemented as instances of this class.
* 
* Strings are constant; their values cannot be changed after they
* are created. String buffers support mutable strings.
* Because String objects are immutable they can be shared. For example:
* <blockquote><pre>
* String str = "abc";
* </pre></blockquote>
* is equivalent to:
* <blockquote><pre>
* char data[] = {'a', 'b', 'c'};
* String str = new String(data);
* </pre></blockquote>
* Here are some more examples of how strings can be used:
* <blockquote><pre>
* System.out.println("abc");
* String cde = "cde";
* System.out.println("abc" + cde);
* String c = "abc".substring(2, 3);
* String d = cde.substring(1, 2);
* </pre></blockquote>
* 
* The class {@code String} includes methods for examining
* individual characters of the sequence, for comparing strings, for
* searching strings, for extracting substrings, and for creating a
* copy of a string with all characters translated to uppercase or to
* lowercase. Case mapping is based on the Unicode Standard version
* specified by the {@link java.lang.Character Character} class.
* 
* The Java language provides special support for the string
* concatenation operator ( + ), and for conversion of
* other objects to strings. For additional information on string
* concatenation and conversion, see The Java Language Specification.
*
* Unless otherwise noted, passing a {@code null} argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* A {@code String} represents a string in the UTF-16 format
* in which supplementary characters are represented by surrogate
* pairs (see the section <a href="Character.html#unicode">Unicode
* Character Representations</a> in the {@code Character} class for
* more information).
* Index values refer to {@code char} code units, so a supplementary
* character uses two positions in a {@code String}.
* The {@code String} class provides methods for dealing with
* Unicode code points (i.e., characters), in addition to those for
* dealing with Unicode code units (i.e., {@code char} values).
*
* Unless otherwise noted, methods for comparing Strings do not take locale
* into account. The {@link java.text.Collator} class provides methods for
* finer-grain, locale-sensitive String comparison.
*
* @implNote The implementation of the string concatenation operator is left to
* the discretion of a Java compiler, as long as the compiler ultimately conforms
* to The Java Language Specification. For example, the {@code javac} compiler
* may implement the operator with {@code StringBuffer}, {@code StringBuilder},
* or {@code java.lang.invoke.StringConcatFactory} depending on the JDK version. The
* implementation of string conversion is typically through the method {@code toString},
* defined by {@code Object} and inherited by all classes in Java.
*
* @author Lee Boynton
* @author Arthur van Hoff
* @author Martin Buchholz
* @author Ulf Zibis
* @see java.lang.Object#toString()
* @see java.lang.StringBuffer
* @see java.lang.StringBuilder
* @see java.nio.charset.Charset
* @since 1.0
* @jls 15.18.1 String Concatenation Operator +
*/

public final class String
 implements java.io.Serializable, Comparable<String>, CharSequence,
 Constable, ConstantDesc {

 /**
 * The value is used for character storage.
 *
 * @implNote This field is trusted by the VM, and is a subject to
 * constant folding if String instance is constant. Overwriting this
 * field after construction will cause problems.
 *
 * Additionally, it is marked with {@link Stable} to trust the contents
 * of the array. No other facility in JDK provides this functionality (yet).
 * {@link Stable} is safe here, because value is never null.
 */
 @Stable
 private final byte[] value;

 /**
 * The identifier of the encoding used to encode the bytes in
 * {@code value}. The supported values in this implementation are
 *
 * LATIN1
 * UTF16
 *
 * @implNote This field is trusted by the VM, and is a subject to
 * constant folding if String instance is constant. Overwriting this
 * field after construction will cause problems.
 */
 private final byte coder;

 /** Cache the hash code for the string */
 private int hash; // Default to 0

 /**
 * Cache if the hash has been calculated as actually being zero, enabling
 * us to avoid recalculating this.
 */
 private boolean hashIsZero; // Default to false;

 /** use serialVersionUID from JDK 1.0.2 for interoperability */
 @java.io.Serial
 private static final long serialVersionUID = -6849794470754667710L;

 /**
 * If String compaction is disabled, the bytes in {@code value} are
 * always encoded in UTF16.
 *
 * For methods with several possible implementation paths, when String
 * compaction is disabled, only one code path is taken.
 *
 * The instance field value is generally opaque to optimizing JIT
 * compilers. Therefore, in performance-sensitive place, an explicit
 * check of the static boolean {@code COMPACT_STRINGS} is done first
 * before checking the {@code coder} field since the static boolean
 * {@code COMPACT_STRINGS} would be constant folded away by an
 * optimizing JIT compiler. The idioms for these cases are as follows.
 *
 * For code such as:
 *
 * if (coder == LATIN1) { ... }
 *
 * can be written more optimally as
 *
 * if (coder() == LATIN1) { ... }
 *
 * or:
 *
 * if (COMPACT_STRINGS && coder == LATIN1) { ... }
 *
 * An optimizing JIT compiler can fold the above conditional as:
 *
 * COMPACT_STRINGS == true => if (coder == LATIN1) { ... }
 * COMPACT_STRINGS == false => if (false) { ... }
 *
 * @implNote
 * The actual value for this field is injected by JVM. The static
 * initialization block is used to set the value here to communicate
 * that this static final field is not statically foldable, and to
 * avoid any possible circular dependency during vm initialization.
 */
 static final boolean COMPACT_STRINGS;

 static {
 COMPACT_STRINGS = true;
 }

 /**
 * Class String is special cased within the Serialization Stream Protocol.
 *
 * A String instance is written into an ObjectOutputStream according to
 * <a href="{@docRoot}/../specs/serialization/protocol.html#stream-elements">
 * <cite>Java Object Serialization Specification</cite>, Section 6.2, "Stream Elements"</a>
 */
 @java.io.Serial
 private static final ObjectStreamField[] serialPersistentFields =
 new ObjectStreamField[0];

 /**
 * Initializes a newly created {@code String} object so that it represents
 * an empty character sequence. Note that use of this constructor is
 * unnecessary since Strings are immutable.
 */
 public String() {
 this.value = "".value;
 this.coder = "".coder;
 }

 /**
 * Initializes a newly created {@code String} object so that it represents
 * the same sequence of characters as the argument; in other words, the
 * newly created string is a copy of the argument string. Unless an
 * explicit copy of {@code original} is needed, use of this constructor is
 * unnecessary since Strings are immutable.
 *
 * @param original
 * A {@code String}
 */
 @IntrinsicCandidate
 public String(String original) {
 this.value = original.value;
 this.coder = original.coder;
 this.hash = original.hash;
 this.hashIsZero = original.hashIsZero;
 }

 /**
 * Allocates a new {@code String} so that it represents the sequence of
 * characters currently contained in the character array argument. The
 * contents of the character array are copied; subsequent modification of
 * the character array does not affect the newly created string.
 *
 * @param value
 * The initial value of the string
 */
 public String(char[] value) {
 this(value, 0, value.length, null);
 }

 /**
 * Allocates a new {@code String} that contains characters from a subarray
 * of the character array argument. The {@code offset} argument is the
 * index of the first character of the subarray and the {@code count}
 * argument specifies the length of the subarray. The contents of the
 * subarray are copied; subsequent modification of the character array does
 * not affect the newly created string.
 *
 * @param value
 * Array that is the source of characters
 *
 * @param offset
 * The initial offset
 *
 * @param count
 * The length
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code count} is negative, or
 * {@code offset} is greater than {@code value.length - count}
 */
 public String(char[] value, int offset, int count) {
 this(value, offset, count, rangeCheck(value, offset, count));
 }

 private static Void rangeCheck(char[] value, int offset, int count) {
 checkBoundsOffCount(offset, count, value.length);
 return null;
 }

 /**
 * Allocates a new {@code String} that contains characters from a subarray
 * of the <a href="Character.html#unicode">Unicode code point</a> array
 * argument. The {@code offset} argument is the index of the first code
 * point of the subarray and the {@code count} argument specifies the
 * length of the subarray. The contents of the subarray are converted to
 * {@code char}s; subsequent modification of the {@code int} array does not
 * affect the newly created string.
 *
 * @param codePoints
 * Array that is the source of Unicode code points
 *
 * @param offset
 * The initial offset
 *
 * @param count
 * The length
 *
 * @throws IllegalArgumentException
 * If any invalid Unicode code point is found in {@code
 * codePoints}
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code count} is negative, or
 * {@code offset} is greater than {@code codePoints.length - count}
 *
 * @since 1.5
 */
 public String(int[] codePoints, int offset, int count) {
 checkBoundsOffCount(offset, count, codePoints.length);
 if (count == 0) {
 this.value = "".value;
 this.coder = "".coder;
 return;
 }
 if (COMPACT_STRINGS) {
 byte[] val = StringLatin1.toBytes(codePoints, offset, count);
 if (val != null) {
 this.coder = LATIN1;
 this.value = val;
 return;
 }
 }
 this.coder = UTF16;
 this.value = StringUTF16.toBytes(codePoints, offset, count);
 }

 /**
 * Allocates a new {@code String} constructed from a subarray of an array
 * of 8-bit integer values.
 *
 * The {@code offset} argument is the index of the first byte of the
 * subarray, and the {@code count} argument specifies the length of the
 * subarray.
 *
 * Each {@code byte} in the subarray is converted to a {@code char} as
 * specified in the {@link #String(byte[],int) String(byte[],int)} constructor.
 *
 * @deprecated This method does not properly convert bytes into characters.
 * As of JDK 1.1, the preferred way to do this is via the
 * {@code String} constructors that take a {@link Charset}, charset name,
 * or that use the {@link Charset#defaultCharset() default charset}.
 *
 * @param ascii
 * The bytes to be converted to characters
 *
 * @param hibyte
 * The top 8 bits of each 16-bit Unicode code unit
 *
 * @param offset
 * The initial offset
 * @param count
 * The length
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code count} is negative, or
 * {@code offset} is greater than {@code ascii.length - count}
 *
 * @see #String(byte[], int)
 * @see #String(byte[], int, int, java.lang.String)
 * @see #String(byte[], int, int, java.nio.charset.Charset)
 * @see #String(byte[], int, int)
 * @see #String(byte[], java.lang.String)
 * @see #String(byte[], java.nio.charset.Charset)
 * @see #String(byte[])
 */
 @Deprecated(since="1.1")
 public String(byte[] ascii, int hibyte, int offset, int count) {
 checkBoundsOffCount(offset, count, ascii.length);
 if (count == 0) {
 this.value = "".value;
 this.coder = "".coder;
 return;
 }
 if (COMPACT_STRINGS && (byte)hibyte == 0) {
 this.value = Arrays.copyOfRange(ascii, offset, offset + count);
 this.coder = LATIN1;
 } else {
 hibyte <<= 8;
 byte[] val = StringUTF16.newBytesFor(count);
 for (int i = 0; i < count; i++) {
 StringUTF16.putChar(val, i, hibyte | (ascii[offset++] & 0xff));
 }
 this.value = val;
 this.coder = UTF16;
 }
 }

 /**
 * Allocates a new {@code String} containing characters constructed from
 * an array of 8-bit integer values. Each character c in the
 * resulting string is constructed from the corresponding component
 * b in the byte array such that:
 *
 * <blockquote><pre>
 * c == (char)(((hibyte & 0xff) << 8)
 * | (b & 0xff))
 * </pre></blockquote>
 *
 * @deprecated This method does not properly convert bytes into
 * characters. As of JDK 1.1, the preferred way to do this is via the
 * {@code String} constructors that take a {@link Charset}, charset name,
 * or that use the {@link Charset#defaultCharset() default charset}.
 *
 * @param ascii
 * The bytes to be converted to characters
 *
 * @param hibyte
 * The top 8 bits of each 16-bit Unicode code unit
 *
 * @see #String(byte[], int, int, java.lang.String)
 * @see #String(byte[], int, int, java.nio.charset.Charset)
 * @see #String(byte[], int, int)
 * @see #String(byte[], java.lang.String)
 * @see #String(byte[], java.nio.charset.Charset)
 * @see #String(byte[])
 */
 @Deprecated(since="1.1")
 public String(byte[] ascii, int hibyte) {
 this(ascii, hibyte, 0, ascii.length);
 }

 /**
 * Constructs a new {@code String} by decoding the specified subarray of
 * bytes using the specified charset. The length of the new {@code String}
 * is a function of the charset, and hence may not be equal to the length
 * of the subarray.
 *
 * The behavior of this constructor when the given bytes are not valid
 * in the given charset is unspecified. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @param offset
 * The index of the first byte to decode
 *
 * @param length
 * The number of bytes to decode
 *
 * @param charsetName
 * The name of a supported {@linkplain java.nio.charset.Charset
 * charset}
 *
 * @throws UnsupportedEncodingException
 * If the named charset is not supported
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code length} is negative, or
 * {@code offset} is greater than {@code bytes.length - length}
 *
 * @since 1.1
 */
 public String(byte[] bytes, int offset, int length, String charsetName)
 throws UnsupportedEncodingException {
 this(lookupCharset(charsetName), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
 }

 /**
 * Constructs a new {@code String} by decoding the specified subarray of
 * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
 * The length of the new {@code String} is a function of the charset, and
 * hence may not be equal to the length of the subarray.
 *
 * This method always replaces malformed-input and unmappable-character
 * sequences with this charset's default replacement string. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @param offset
 * The index of the first byte to decode
 *
 * @param length
 * The number of bytes to decode
 *
 * @param charset
 * The {@linkplain java.nio.charset.Charset charset} to be used to
 * decode the {@code bytes}
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code length} is negative, or
 * {@code offset} is greater than {@code bytes.length - length}
 *
 * @since 1.6
 */
 public String(byte[] bytes, int offset, int length, Charset charset) {
 this(Objects.requireNonNull(charset), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
 }

 /**
 * This method does not do any precondition checks on its arguments.
 * 
 * Important: parameter order of this method is deliberately changed in order to
 * disambiguate it against other similar methods of this class.
 */
 @SuppressWarnings("removal")
 private String(Charset charset, byte[] bytes, int offset, int length) {
 if (length == 0) {
 this.value = "".value;
 this.coder = "".coder;
 } else if (charset == UTF_8.INSTANCE) {
 if (COMPACT_STRINGS) {
 int dp = StringCoding.countPositives(bytes, offset, length);
 if (dp == length) {
 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
 this.coder = LATIN1;
 return;
 }
 int sl = offset + length;
 byte[] dst = new byte[length];
 if (dp > 0) {
 System.arraycopy(bytes, offset, dst, 0, dp);
 offset += dp;
 }
 while (offset < sl) {
 int b1 = bytes[offset++];
 if (b1 >= 0) {
 dst[dp++] = (byte)b1;
 continue;
 }
 if ((b1 & 0xfe) == 0xc2 && offset < sl) { // b1 either 0xc2 or 0xc3
 int b2 = bytes[offset];
 if (b2 < -64) { // continuation bytes are always negative values in the range -128 to -65
 dst[dp++] = (byte)decode2(b1, b2);
 offset++;
 continue;
 }
 }
 // anything not a latin1, including the REPL
 // we have to go with the utf16
 offset--;
 break;
 }
 if (offset == sl) {
 if (dp != dst.length) {
 dst = Arrays.copyOf(dst, dp);
 }
 this.value = dst;
 this.coder = LATIN1;
 return;
 }
 byte[] buf = new byte[length << 1];
 StringLatin1.inflate(dst, 0, buf, 0, dp);
 dst = buf;
 dp = decodeUTF8_UTF16(bytes, offset, sl, dst, dp, true);
 if (dp != length) {
 dst = Arrays.copyOf(dst, dp << 1);
 }
 this.value = dst;
 this.coder = UTF16;
 } else { // !COMPACT_STRINGS
 byte[] dst = new byte[length << 1];
 int dp = decodeUTF8_UTF16(bytes, offset, offset + length, dst, 0, true);
 if (dp != length) {
 dst = Arrays.copyOf(dst, dp << 1);
 }
 this.value = dst;
 this.coder = UTF16;
 }
 } else if (charset == ISO_8859_1.INSTANCE) {
 if (COMPACT_STRINGS) {
 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
 this.coder = LATIN1;
 } else {
 this.value = StringLatin1.inflate(bytes, offset, length);
 this.coder = UTF16;
 }
 } else if (charset == US_ASCII.INSTANCE) {
 if (COMPACT_STRINGS && !StringCoding.hasNegatives(bytes, offset, length)) {
 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
 this.coder = LATIN1;
 } else {
 byte[] dst = new byte[length << 1];
 int dp = 0;
 while (dp < length) {
 int b = bytes[offset++];
 StringUTF16.putChar(dst, dp++, (b >= 0) ? (char) b : REPL);
 }
 this.value = dst;
 this.coder = UTF16;
 }
 } else {
 // (1)We never cache the "external" cs, the only benefit of creating
 // an additional StringDe/Encoder object to wrap it is to share the
 // de/encode() method. These SD/E objects are short-lived, the young-gen
 // gc should be able to take care of them well. But the best approach
 // is still not to generate them if not really necessary.
 // (2)The defensive copy of the input byte/char[] has a big performance
 // impact, as well as the outgoing result byte/char[]. Need to do the
 // optimization check of (sm==null && classLoader0==null) for both.
 CharsetDecoder cd = charset.newDecoder();
 // ArrayDecoder fastpaths
 if (cd instanceof ArrayDecoder ad) {
 // ascii
 if (ad.isASCIICompatible() && !StringCoding.hasNegatives(bytes, offset, length)) {
 if (COMPACT_STRINGS) {
 this.value = Arrays.copyOfRange(bytes, offset, offset + length);
 this.coder = LATIN1;
 return;
 }
 this.value = StringLatin1.inflate(bytes, offset, length);
 this.coder = UTF16;
 return;
 }

 // fastpath for always Latin1 decodable single byte
 if (COMPACT_STRINGS && ad.isLatin1Decodable()) {
 byte[] dst = new byte[length];
 ad.decodeToLatin1(bytes, offset, length, dst);
 this.value = dst;
 this.coder = LATIN1;
 return;
 }

 int en = scale(length, cd.maxCharsPerByte());
 cd.onMalformedInput(CodingErrorAction.REPLACE)
 .onUnmappableCharacter(CodingErrorAction.REPLACE);
 char[] ca = new char[en];
 int clen = ad.decode(bytes, offset, length, ca);
 if (COMPACT_STRINGS) {
 byte[] bs = StringUTF16.compress(ca, 0, clen);
 if (bs != null) {
 value = bs;
 coder = LATIN1;
 return;
 }
 }
 coder = UTF16;
 value = StringUTF16.toBytes(ca, 0, clen);
 return;
 }

 // decode using CharsetDecoder
 int en = scale(length, cd.maxCharsPerByte());
 cd.onMalformedInput(CodingErrorAction.REPLACE)
 .onUnmappableCharacter(CodingErrorAction.REPLACE);
 char[] ca = new char[en];
 if (charset.getClass().getClassLoader0() != null &&
 System.getSecurityManager() != null) {
 bytes = Arrays.copyOfRange(bytes, offset, offset + length);
 offset = 0;
 }

 int caLen;
 try {
 caLen = decodeWithDecoder(cd, ca, bytes, offset, length);
 } catch (CharacterCodingException x) {
 // Substitution is enabled, so this shouldn't happen
 throw new Error(x);
 }
 if (COMPACT_STRINGS) {
 byte[] bs = StringUTF16.compress(ca, 0, caLen);
 if (bs != null) {
 value = bs;
 coder = LATIN1;
 return;
 }
 }
 coder = UTF16;
 value = StringUTF16.toBytes(ca, 0, caLen);
 }
 }

 /*
 * Throws iae, instead of replacing, if malformed or unmappable.
 */
 static String newStringUTF8NoRepl(byte[] bytes, int offset, int length) {
 checkBoundsOffCount(offset, length, bytes.length);
 if (length == 0) {
 return "";
 }
 int dp;
 byte[] dst;
 if (COMPACT_STRINGS) {
 dp = StringCoding.countPositives(bytes, offset, length);
 int sl = offset + length;
 if (dp == length) {
 return new String(Arrays.copyOfRange(bytes, offset, offset + length), LATIN1);
 }
 dst = new byte[length];
 System.arraycopy(bytes, offset, dst, 0, dp);
 offset += dp;
 while (offset < sl) {
 int b1 = bytes[offset++];
 if (b1 >= 0) {
 dst[dp++] = (byte)b1;
 continue;
 }
 if ((b1 & 0xfe) == 0xc2 && offset < sl) { // b1 either 0xc2 or 0xc3
 int b2 = bytes[offset];
 if (b2 < -64) { // continuation bytes are always negative values in the range -128 to -65
 dst[dp++] = (byte)decode2(b1, b2);
 offset++;
 continue;
 }
 }
 // anything not a latin1, including the REPL
 // we have to go with the utf16
 offset--;
 break;
 }
 if (offset == sl) {
 if (dp != dst.length) {
 dst = Arrays.copyOf(dst, dp);
 }
 return new String(dst, LATIN1);
 }
 if (dp == 0) {
 dst = new byte[length << 1];
 } else {
 byte[] buf = new byte[length << 1];
 StringLatin1.inflate(dst, 0, buf, 0, dp);
 dst = buf;
 }
 dp = decodeUTF8_UTF16(bytes, offset, sl, dst, dp, false);
 } else { // !COMPACT_STRINGS
 dst = new byte[length << 1];
 dp = decodeUTF8_UTF16(bytes, offset, offset + length, dst, 0, false);
 }
 if (dp != length) {
 dst = Arrays.copyOf(dst, dp << 1);
 }
 return new String(dst, UTF16);
 }

 static String newStringNoRepl(byte[] src, Charset cs) throws CharacterCodingException {
 try {
 return newStringNoRepl1(src, cs);
 } catch (IllegalArgumentException e) {
 //newStringNoRepl1 throws IAE with MalformedInputException or CCE as the cause
 Throwable cause = e.getCause();
 if (cause instanceof MalformedInputException mie) {
 throw mie;
 }
 throw (CharacterCodingException)cause;
 }
 }

 @SuppressWarnings("removal")
 private static String newStringNoRepl1(byte[] src, Charset cs) {
 int len = src.length;
 if (len == 0) {
 return "";
 }
 if (cs == UTF_8.INSTANCE) {
 return newStringUTF8NoRepl(src, 0, src.length);
 }
 if (cs == ISO_8859_1.INSTANCE) {
 if (COMPACT_STRINGS)
 return new String(src, LATIN1);
 return new String(StringLatin1.inflate(src, 0, src.length), UTF16);
 }
 if (cs == US_ASCII.INSTANCE) {
 if (!StringCoding.hasNegatives(src, 0, src.length)) {
 if (COMPACT_STRINGS)
 return new String(src, LATIN1);
 return new String(StringLatin1.inflate(src, 0, src.length), UTF16);
 } else {
 throwMalformed(src);
 }
 }

 CharsetDecoder cd = cs.newDecoder();
 // ascii fastpath
 if (cd instanceof ArrayDecoder ad &&
 ad.isASCIICompatible() &&
 !StringCoding.hasNegatives(src, 0, src.length)) {
 return new String(src, 0, src.length, ISO_8859_1.INSTANCE);
 }
 int en = scale(len, cd.maxCharsPerByte());
 char[] ca = new char[en];
 if (cs.getClass().getClassLoader0() != null &&
 System.getSecurityManager() != null) {
 src = Arrays.copyOf(src, len);
 }
 int caLen;
 try {
 caLen = decodeWithDecoder(cd, ca, src, 0, src.length);
 } catch (CharacterCodingException x) {
 // throw via IAE
 throw new IllegalArgumentException(x);
 }
 if (COMPACT_STRINGS) {
 byte[] bs = StringUTF16.compress(ca, 0, caLen);
 if (bs != null) {
 return new String(bs, LATIN1);
 }
 }
 return new String(StringUTF16.toBytes(ca, 0, caLen), UTF16);
 }

 private static final char REPL = '\ufffd';

 // Trim the given byte array to the given length
 @SuppressWarnings("removal")
 private static byte[] safeTrim(byte[] ba, int len, boolean isTrusted) {
 if (len == ba.length && (isTrusted || System.getSecurityManager() == null)) {
 return ba;
 } else {
 return Arrays.copyOf(ba, len);
 }
 }

 private static int scale(int len, float expansionFactor) {
 // We need to perform double, not float, arithmetic; otherwise
 // we lose low order bits when len is larger than 2**24.
 return (int)(len * (double)expansionFactor);
 }

 private static Charset lookupCharset(String csn) throws UnsupportedEncodingException {
 Objects.requireNonNull(csn);
 try {
 return Charset.forName(csn);
 } catch (UnsupportedCharsetException | IllegalCharsetNameException x) {
 throw new UnsupportedEncodingException(csn);
 }
 }

 private static byte[] encode(Charset cs, byte coder, byte[] val) {
 if (cs == UTF_8.INSTANCE) {
 return encodeUTF8(coder, val, true);
 }
 if (cs == ISO_8859_1.INSTANCE) {
 return encode8859_1(coder, val);
 }
 if (cs == US_ASCII.INSTANCE) {
 return encodeASCII(coder, val);
 }
 return encodeWithEncoder(cs, coder, val, true);
 }

 private static byte[] encodeWithEncoder(Charset cs, byte coder, byte[] val, boolean doReplace) {
 CharsetEncoder ce = cs.newEncoder();
 int len = val.length >> coder; // assume LATIN1=0/UTF16=1;
 int en = scale(len, ce.maxBytesPerChar());
 // fastpath with ArrayEncoder implies `doReplace`.
 if (doReplace && ce instanceof ArrayEncoder ae) {
 // fastpath for ascii compatible
 if (coder == LATIN1 &&
 ae.isASCIICompatible() &&
 !StringCoding.hasNegatives(val, 0, val.length)) {
 return Arrays.copyOf(val, val.length);
 }
 byte[] ba = new byte[en];
 if (len == 0) {
 return ba;
 }

 int blen = (coder == LATIN1) ? ae.encodeFromLatin1(val, 0, len, ba)
 : ae.encodeFromUTF16(val, 0, len, ba);
 if (blen != -1) {
 return safeTrim(ba, blen, true);
 }
 }

 byte[] ba = new byte[en];
 if (len == 0) {
 return ba;
 }
 if (doReplace) {
 ce.onMalformedInput(CodingErrorAction.REPLACE)
 .onUnmappableCharacter(CodingErrorAction.REPLACE);
 }
 char[] ca = (coder == LATIN1 ) ? StringLatin1.toChars(val)
 : StringUTF16.toChars(val);
 ByteBuffer bb = ByteBuffer.wrap(ba);
 CharBuffer cb = CharBuffer.wrap(ca, 0, len);
 try {
 CoderResult cr = ce.encode(cb, bb, true);
 if (!cr.isUnderflow())
 cr.throwException();
 cr = ce.flush(bb);
 if (!cr.isUnderflow())
 cr.throwException();
 } catch (CharacterCodingException x) {
 if (!doReplace) {
 throw new IllegalArgumentException(x);
 } else {
 throw new Error(x);
 }
 }
 return safeTrim(ba, bb.position(), cs.getClass().getClassLoader0() == null);
 }

 /*
 * Throws iae, instead of replacing, if unmappable.
 */
 static byte[] getBytesUTF8NoRepl(String s) {
 return encodeUTF8(s.coder(), s.value(), false);
 }

 private static boolean isASCII(byte[] src) {
 return !StringCoding.hasNegatives(src, 0, src.length);
 }

 /*
 * Throws CCE, instead of replacing, if unmappable.
 */
 static byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException {
 try {
 return getBytesNoRepl1(s, cs);
 } catch (IllegalArgumentException e) {
 //getBytesNoRepl1 throws IAE with UnmappableCharacterException or CCE as the cause
 Throwable cause = e.getCause();
 if (cause instanceof UnmappableCharacterException) {
 throw (UnmappableCharacterException)cause;
 }
 throw (CharacterCodingException)cause;
 }
 }

 private static byte[] getBytesNoRepl1(String s, Charset cs) {
 byte[] val = s.value();
 byte coder = s.coder();
 if (cs == UTF_8.INSTANCE) {
 if (coder == LATIN1 && isASCII(val)) {
 return val;
 }
 return encodeUTF8(coder, val, false);
 }
 if (cs == ISO_8859_1.INSTANCE) {
 if (coder == LATIN1) {
 return val;
 }
 return encode8859_1(coder, val, false);
 }
 if (cs == US_ASCII.INSTANCE) {
 if (coder == LATIN1) {
 if (isASCII(val)) {
 return val;
 } else {
 throwUnmappable(val);
 }
 }
 }
 return encodeWithEncoder(cs, coder, val, false);
 }

 private static byte[] encodeASCII(byte coder, byte[] val) {
 if (coder == LATIN1) {
 byte[] dst = Arrays.copyOf(val, val.length);
 for (int i = 0; i < dst.length; i++) {
 if (dst[i] < 0) {
 dst[i] = '?';
 }
 }
 return dst;
 }
 int len = val.length >> 1;
 byte[] dst = new byte[len];
 int dp = 0;
 for (int i = 0; i < len; i++) {
 char c = StringUTF16.getChar(val, i);
 if (c < 0x80) {
 dst[dp++] = (byte)c;
 continue;
 }
 if (Character.isHighSurrogate(c) && i + 1 < len &&
 Character.isLowSurrogate(StringUTF16.getChar(val, i + 1))) {
 i++;
 }
 dst[dp++] = '?';
 }
 if (len == dp) {
 return dst;
 }
 return Arrays.copyOf(dst, dp);
 }

 private static byte[] encode8859_1(byte coder, byte[] val) {
 return encode8859_1(coder, val, true);
 }

 private static byte[] encode8859_1(byte coder, byte[] val, boolean doReplace) {
 if (coder == LATIN1) {
 return Arrays.copyOf(val, val.length);
 }
 int len = val.length >> 1;
 byte[] dst = new byte[len];
 int dp = 0;
 int sp = 0;
 int sl = len;
 while (sp < sl) {
 int ret = StringCoding.implEncodeISOArray(val, sp, dst, dp, len);
 sp = sp + ret;
 dp = dp + ret;
 if (ret != len) {
 if (!doReplace) {
 throwUnmappable(sp);
 }
 char c = StringUTF16.getChar(val, sp++);
 if (Character.isHighSurrogate(c) && sp < sl &&
 Character.isLowSurrogate(StringUTF16.getChar(val, sp))) {
 sp++;
 }
 dst[dp++] = '?';
 len = sl - sp;
 }
 }
 if (dp == dst.length) {
 return dst;
 }
 return Arrays.copyOf(dst, dp);
 }

 //////////////////////////////// utf8 ////////////////////////////////////

 /**
 * Decodes ASCII from the source byte array into the destination
 * char array. Used via JavaLangAccess from UTF_8 and other charset
 * decoders.
 *
 * @return the number of bytes successfully decoded, at most len
 */
 /* package-private */
 static int decodeASCII(byte[] sa, int sp, char[] da, int dp, int len) {
 int count = StringCoding.countPositives(sa, sp, len);
 while (count < len) {
 if (sa[sp + count] < 0) {
 break;
 }
 count++;
 }
 StringLatin1.inflate(sa, sp, da, dp, count);
 return count;
 }

 private static boolean isNotContinuation(int b) {
 return (b & 0xc0) != 0x80;
 }

 private static boolean isMalformed3(int b1, int b2, int b3) {
 return (b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
 (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80;
 }

 private static boolean isMalformed3_2(int b1, int b2) {
 return (b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
 (b2 & 0xc0) != 0x80;
 }

 private static boolean isMalformed4(int b2, int b3, int b4) {
 return (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80 ||
 (b4 & 0xc0) != 0x80;
 }

 private static boolean isMalformed4_2(int b1, int b2) {
 return (b1 == 0xf0 && (b2 < 0x90 || b2 > 0xbf)) ||
 (b1 == 0xf4 && (b2 & 0xf0) != 0x80) ||
 (b2 & 0xc0) != 0x80;
 }

 private static boolean isMalformed4_3(int b3) {
 return (b3 & 0xc0) != 0x80;
 }

 private static char decode2(int b1, int b2) {
 return (char)(((b1 << 6) ^ b2) ^
 (((byte) 0xC0 << 6) ^
 ((byte) 0x80 << 0)));
 }

 private static char decode3(int b1, int b2, int b3) {
 return (char)((b1 << 12) ^
 (b2 << 6) ^
 (b3 ^
 (((byte) 0xE0 << 12) ^
 ((byte) 0x80 << 6) ^
 ((byte) 0x80 << 0))));
 }

 private static int decode4(int b1, int b2, int b3, int b4) {
 return ((b1 << 18) ^
 (b2 << 12) ^
 (b3 << 6) ^
 (b4 ^
 (((byte) 0xF0 << 18) ^
 ((byte) 0x80 << 12) ^
 ((byte) 0x80 << 6) ^
 ((byte) 0x80 << 0))));
 }

 private static int decodeUTF8_UTF16(byte[] src, int sp, int sl, byte[] dst, int dp, boolean doReplace) {
 while (sp < sl) {
 int b1 = src[sp++];
 if (b1 >= 0) {
 StringUTF16.putChar(dst, dp++, (char) b1);
 } else if ((b1 >> 5) == -2 && (b1 & 0x1e) != 0) {
 if (sp < sl) {
 int b2 = src[sp++];
 if (isNotContinuation(b2)) {
 if (!doReplace) {
 throwMalformed(sp - 1, 1);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 sp--;
 } else {
 StringUTF16.putChar(dst, dp++, decode2(b1, b2));
 }
 continue;
 }
 if (!doReplace) {
 throwMalformed(sp, 1); // underflow()
 }
 StringUTF16.putChar(dst, dp++, REPL);
 break;
 } else if ((b1 >> 4) == -2) {
 if (sp + 1 < sl) {
 int b2 = src[sp++];
 int b3 = src[sp++];
 if (isMalformed3(b1, b2, b3)) {
 if (!doReplace) {
 throwMalformed(sp - 3, 3);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 sp -= 3;
 sp += malformed3(src, sp);
 } else {
 char c = decode3(b1, b2, b3);
 if (Character.isSurrogate(c)) {
 if (!doReplace) {
 throwMalformed(sp - 3, 3);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 } else {
 StringUTF16.putChar(dst, dp++, c);
 }
 }
 continue;
 }
 if (sp < sl && isMalformed3_2(b1, src[sp])) {
 if (!doReplace) {
 throwMalformed(sp - 1, 2);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 continue;
 }
 if (!doReplace) {
 throwMalformed(sp, 1);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 break;
 } else if ((b1 >> 3) == -2) {
 if (sp + 2 < sl) {
 int b2 = src[sp++];
 int b3 = src[sp++];
 int b4 = src[sp++];
 int uc = decode4(b1, b2, b3, b4);
 if (isMalformed4(b2, b3, b4) ||
 !Character.isSupplementaryCodePoint(uc)) { // shortest form check
 if (!doReplace) {
 throwMalformed(sp - 4, 4);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 sp -= 4;
 sp += malformed4(src, sp);
 } else {
 StringUTF16.putChar(dst, dp++, Character.highSurrogate(uc));
 StringUTF16.putChar(dst, dp++, Character.lowSurrogate(uc));
 }
 continue;
 }
 b1 &= 0xff;
 if (b1 > 0xf4 || sp < sl && isMalformed4_2(b1, src[sp] & 0xff)) {
 if (!doReplace) {
 throwMalformed(sp - 1, 1); // or 2
 }
 StringUTF16.putChar(dst, dp++, REPL);
 continue;
 }
 if (!doReplace) {
 throwMalformed(sp - 1, 1);
 }
 sp++;
 StringUTF16.putChar(dst, dp++, REPL);
 if (sp < sl && isMalformed4_3(src[sp])) {
 continue;
 }
 break;
 } else {
 if (!doReplace) {
 throwMalformed(sp - 1, 1);
 }
 StringUTF16.putChar(dst, dp++, REPL);
 }
 }
 return dp;
 }

 private static int decodeWithDecoder(CharsetDecoder cd, char[] dst, byte[] src, int offset, int length)
 throws CharacterCodingException {
 ByteBuffer bb = ByteBuffer.wrap(src, offset, length);
 CharBuffer cb = CharBuffer.wrap(dst, 0, dst.length);
 CoderResult cr = cd.decode(bb, cb, true);
 if (!cr.isUnderflow())
 cr.throwException();
 cr = cd.flush(cb);
 if (!cr.isUnderflow())
 cr.throwException();
 return cb.position();
 }

 private static int malformed3(byte[] src, int sp) {
 int b1 = src[sp++];
 int b2 = src[sp]; // no need to lookup b3
 return ((b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
 isNotContinuation(b2)) ? 1 : 2;
 }

 private static int malformed4(byte[] src, int sp) {
 // we don't care the speed here
 int b1 = src[sp++] & 0xff;
 int b2 = src[sp++] & 0xff;
 if (b1 > 0xf4 ||
 (b1 == 0xf0 && (b2 < 0x90 || b2 > 0xbf)) ||
 (b1 == 0xf4 && (b2 & 0xf0) != 0x80) ||
 isNotContinuation(b2))
 return 1;
 if (isNotContinuation(src[sp]))
 return 2;
 return 3;
 }

 private static void throwMalformed(int off, int nb) {
 String msg = "malformed input off : " + off + ", length : " + nb;
 throw new IllegalArgumentException(msg, new MalformedInputException(nb));
 }

 private static void throwMalformed(byte[] val) {
 int dp = 0;
 while (dp < val.length && val[dp] >=0) { dp++; }
 throwMalformed(dp, 1);
 }

 private static void throwUnmappable(int off) {
 String msg = "malformed input off : " + off + ", length : 1";
 throw new IllegalArgumentException(msg, new UnmappableCharacterException(1));
 }

 private static void throwUnmappable(byte[] val) {
 int dp = 0;
 while (dp < val.length && val[dp] >=0) { dp++; }
 throwUnmappable(dp);
 }

 private static byte[] encodeUTF8(byte coder, byte[] val, boolean doReplace) {
 if (coder == UTF16)
 return encodeUTF8_UTF16(val, doReplace);

 if (!StringCoding.hasNegatives(val, 0, val.length))
 return Arrays.copyOf(val, val.length);

 int dp = 0;
 byte[] dst = new byte[val.length << 1];
 for (byte c : val) {
 if (c < 0) {
 dst[dp++] = (byte) (0xc0 | ((c & 0xff) >> 6));
 dst[dp++] = (byte) (0x80 | (c & 0x3f));
 } else {
 dst[dp++] = c;
 }
 }
 if (dp == dst.length)
 return dst;
 return Arrays.copyOf(dst, dp);
 }

 private static byte[] encodeUTF8_UTF16(byte[] val, boolean doReplace) {
 int dp = 0;
 int sp = 0;
 int sl = val.length >> 1;
 byte[] dst = new byte[sl * 3];
 while (sp < sl) {
 // ascii fast loop;
 char c = StringUTF16.getChar(val, sp);
 if (c >= '\u0080') {
 break;
 }
 dst[dp++] = (byte)c;
 sp++;
 }
 while (sp < sl) {
 char c = StringUTF16.getChar(val, sp++);
 if (c < 0x80) {
 dst[dp++] = (byte)c;
 } else if (c < 0x800) {
 dst[dp++] = (byte)(0xc0 | (c >> 6));
 dst[dp++] = (byte)(0x80 | (c & 0x3f));
 } else if (Character.isSurrogate(c)) {
 int uc = -1;
 char c2;
 if (Character.isHighSurrogate(c) && sp < sl &&
 Character.isLowSurrogate(c2 = StringUTF16.getChar(val, sp))) {
 uc = Character.toCodePoint(c, c2);
 }
 if (uc < 0) {
 if (doReplace) {
 dst[dp++] = '?';
 } else {
 throwUnmappable(sp - 1);
 }
 } else {
 dst[dp++] = (byte)(0xf0 | ((uc >> 18)));
 dst[dp++] = (byte)(0x80 | ((uc >> 12) & 0x3f));
 dst[dp++] = (byte)(0x80 | ((uc >> 6) & 0x3f));
 dst[dp++] = (byte)(0x80 | (uc & 0x3f));
 sp++; // 2 chars
 }
 } else {
 // 3 bytes, 16 bits
 dst[dp++] = (byte)(0xe0 | ((c >> 12)));
 dst[dp++] = (byte)(0x80 | ((c >> 6) & 0x3f));
 dst[dp++] = (byte)(0x80 | (c & 0x3f));
 }
 }
 if (dp == dst.length) {
 return dst;
 }
 return Arrays.copyOf(dst, dp);
 }

 /**
 * Constructs a new {@code String} by decoding the specified array of bytes
 * using the specified {@linkplain java.nio.charset.Charset charset}. The
 * length of the new {@code String} is a function of the charset, and hence
 * may not be equal to the length of the byte array.
 *
 * The behavior of this constructor when the given bytes are not valid
 * in the given charset is unspecified. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @param charsetName
 * The name of a supported {@linkplain java.nio.charset.Charset
 * charset}
 *
 * @throws UnsupportedEncodingException
 * If the named charset is not supported
 *
 * @since 1.1
 */
 public String(byte[] bytes, String charsetName)
 throws UnsupportedEncodingException {
 this(lookupCharset(charsetName), bytes, 0, bytes.length);
 }

 /**
 * Constructs a new {@code String} by decoding the specified array of
 * bytes using the specified {@linkplain java.nio.charset.Charset charset}.
 * The length of the new {@code String} is a function of the charset, and
 * hence may not be equal to the length of the byte array.
 *
 * This method always replaces malformed-input and unmappable-character
 * sequences with this charset's default replacement string. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @param charset
 * The {@linkplain java.nio.charset.Charset charset} to be used to
 * decode the {@code bytes}
 *
 * @since 1.6
 */
 public String(byte[] bytes, Charset charset) {
 this(Objects.requireNonNull(charset), bytes, 0, bytes.length);
 }

 /**
 * Constructs a new {@code String} by decoding the specified subarray of
 * bytes using the {@link Charset#defaultCharset() default charset}.
 * The length of the new {@code String} is a function of the charset,
 * and hence may not be equal to the length of the subarray.
 *
 * The behavior of this constructor when the given bytes are not valid
 * in the default charset is unspecified. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @param offset
 * The index of the first byte to decode
 *
 * @param length
 * The number of bytes to decode
 *
 * @throws IndexOutOfBoundsException
 * If {@code offset} is negative, {@code length} is negative, or
 * {@code offset} is greater than {@code bytes.length - length}
 *
 * @since 1.1
 */
 public String(byte[] bytes, int offset, int length) {
 this(Charset.defaultCharset(), bytes, checkBoundsOffCount(offset, length, bytes.length), length);
 }

 /**
 * Constructs a new {@code String} by decoding the specified array of bytes
 * using the {@link Charset#defaultCharset() default charset}. The length
 * of the new {@code String} is a function of the charset, and hence may not
 * be equal to the length of the byte array.
 *
 * The behavior of this constructor when the given bytes are not valid
 * in the default charset is unspecified. The {@link
 * java.nio.charset.CharsetDecoder} class should be used when more control
 * over the decoding process is required.
 *
 * @param bytes
 * The bytes to be decoded into characters
 *
 * @since 1.1
 */
 public String(byte[] bytes) {
 this(Charset.defaultCharset(), bytes, 0, bytes.length);
 }

 /**
 * Allocates a new string that contains the sequence of characters
 * currently contained in the string buffer argument. The contents of the
 * string buffer are copied; subsequent modification of the string buffer
 * does not affect the newly created string.
 *
 * @param buffer
 * A {@code StringBuffer}
 */
 public String(StringBuffer buffer) {
 this(buffer.toString());
 }

 /**
 * Allocates a new string that contains the sequence of characters
 * currently contained in the string builder argument. The contents of the
 * string builder are copied; subsequent modification of the string builder
 * does not affect the newly created string.
 *
 * This constructor is provided to ease migration to {@code
 * StringBuilder}. Obtaining a string from a string builder via the {@code
 * toString} method is likely to run faster and is generally preferred.
 *
 * @param builder
 * A {@code StringBuilder}
 *
 * @since 1.5
 */
 public String(StringBuilder builder) {
 this(builder, null);
 }

 /**
 * Returns the length of this string.
 * The length is equal to the number of <a href="Character.html#unicode">Unicode
 * code units</a> in the string.
 *
 * @return the length of the sequence of characters represented by this
 * object.
 */
 public int length() {
 return value.length >> coder();
 }

 /**
 * Returns {@code true} if, and only if, {@link #length()} is {@code 0}.
 *
 * @return {@code true} if {@link #length()} is {@code 0}, otherwise
 * {@code false}
 *
 * @since 1.6
 */
 @Override
 public boolean isEmpty() {
 return value.length == 0;
 }

 /**
 * Returns the {@code char} value at the
 * specified index. An index ranges from {@code 0} to
 * {@code length() - 1}. The first {@code char} value of the sequence
 * is at index {@code 0}, the next at index {@code 1},
 * and so on, as for array indexing.
 *
 * If the {@code char} value specified by the index is a
 * <a href="Character.html#unicode">surrogate</a>, the surrogate
 * value is returned.
 *
 * @param index the index of the {@code char} value.
 * @return the {@code char} value at the specified index of this string.
 * The first {@code char} value is at index {@code 0}.
 * @throws IndexOutOfBoundsException if the {@code index}
 * argument is negative or not less than the length of this
 * string.
 */
 public char charAt(int index) {
 if (isLatin1()) {
 return StringLatin1.charAt(value, index);
 } else {
 return StringUTF16.charAt(value, index);
 }
 }

 /**
 * Returns the character (Unicode code point) at the specified
 * index. The index refers to {@code char} values
 * (Unicode code units) and ranges from {@code 0} to
 * {@link #length()}{@code - 1}.
 *
 * If the {@code char} value specified at the given index
 * is in the high-surrogate range, the following index is less
 * than the length of this {@code String}, and the
 * {@code char} value at the following index is in the
 * low-surrogate range, then the supplementary code point
 * corresponding to this surrogate pair is returned. Otherwise,
 * the {@code char} value at the given index is returned.
 *
 * @param index the index to the {@code char} values
 * @return the code point value of the character at the
 * {@code index}
 * @throws IndexOutOfBoundsException if the {@code index}
 * argument is negative or not less than the length of this
 * string.
 * @since 1.5
 */
 public int codePointAt(int index) {
 if (isLatin1()) {
 checkIndex(index, value.length);
 return value[index] & 0xff;
 }
 int length = value.length >> 1;
 checkIndex(index, length);
 return StringUTF16.codePointAt(value, index, length);
 }

 /**
 * Returns the character (Unicode code point) before the specified
 * index. The index refers to {@code char} values
 * (Unicode code units) and ranges from {@code 1} to {@link
 * CharSequence#length() length}.
 *
 * If the {@code char} value at {@code (index - 1)}
 * is in the low-surrogate range, {@code (index - 2)} is not
 * negative, and the {@code char} value at {@code (index -
 * 2)} is in the high-surrogate range, then the
 * supplementary code point value of the surrogate pair is
 * returned. If the {@code char} value at {@code index -
 * 1} is an unpaired low-surrogate or a high-surrogate, the
 * surrogate value is returned.
 *
 * @param index the index following the code point that should be returned
 * @return the Unicode code point value before the given index.
 * @throws IndexOutOfBoundsException if the {@code index}
 * argument is less than 1 or greater than the length
 * of this string.
 * @since 1.5
 */
 public int codePointBefore(int index) {
 int i = index - 1;
 checkIndex(i, length());
 if (isLatin1()) {
 return (value[i] & 0xff);
 }
 return StringUTF16.codePointBefore(value, index);
 }

 /**
 * Returns the number of Unicode code points in the specified text
 * range of this {@code String}. The text range begins at the
 * specified {@code beginIndex} and extends to the
 * {@code char} at index {@code endIndex - 1}. Thus the
 * length (in {@code char}s) of the text range is
 * {@code endIndex-beginIndex}. Unpaired surrogates within
 * the text range count as one code point each.
 *
 * @param beginIndex the index to the first {@code char} of
 * the text range.
 * @param endIndex the index after the last {@code char} of
 * the text range.
 * @return the number of Unicode code points in the specified text
 * range
 * @throws IndexOutOfBoundsException if the
 * {@code beginIndex} is negative, or {@code endIndex}
 * is larger than the length of this {@code String}, or
 * {@code beginIndex} is larger than {@code endIndex}.
 * @since 1.5
 */
 public int codePointCount(int beginIndex, int endIndex) {
 Objects.checkFromToIndex(beginIndex, endIndex, length());
 if (isLatin1()) {
 return endIndex - beginIndex;
 }
 return StringUTF16.codePointCount(value, beginIndex, endIndex);
 }

 /**
 * Returns the index within this {@code String} that is
 * offset from the given {@code index} by
 * {@code codePointOffset} code points. Unpaired surrogates
 * within the text range given by {@code index} and
 * {@code codePointOffset} count as one code point each.
 *
 * @param index the index to be offset
 * @param codePointOffset the offset in code points
 * @return the index within this {@code String}
 * @throws IndexOutOfBoundsException if {@code index}
 * is negative or larger than the length of this
 * {@code String}, or if {@code codePointOffset} is positive
 * and the substring starting with {@code index} has fewer
 * than {@code codePointOffset} code points,
 * or if {@code codePointOffset} is negative and the substring
 * before {@code index} has fewer than the absolute value
 * of {@code codePointOffset} code points.
 * @since 1.5
 */
 public int offsetByCodePoints(int index, int codePointOffset) {
 return Character.offsetByCodePoints(this, index, codePointOffset);
 }

 /**
 * Copies characters from this string into the destination character
 * array.
 * 
 * The first character to be copied is at index {@code srcBegin};
 * the last character to be copied is at index {@code srcEnd-1}
 * (thus the total number of characters to be copied is
 * {@code srcEnd-srcBegin}). The characters are copied into the
 * subarray of {@code dst} starting at index {@code dstBegin}
 * and ending at index:
 * <blockquote><pre>
 * dstBegin + (srcEnd-srcBegin) - 1
 * </pre></blockquote>
 *
 * @param srcBegin index of the first character in the string
 * to copy.
 * @param srcEnd index after the last character in the string
 * to copy.
 * @param dst the destination array.
 * @param dstBegin the start offset in the destination array.
 * @throws IndexOutOfBoundsException If any of the following
 * is true:
 * <ul><li>{@code srcBegin} is negative.
 * <li>{@code srcBegin} is greater than {@code srcEnd}
 * <li>{@code srcEnd} is greater than the length of this
 * string
 * <li>{@code dstBegin} is negative
 * <li>{@code dstBegin+(srcEnd-srcBegin)} is larger than
 * {@code dst.length}</ul>
 */
 public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) {
 checkBoundsBeginEnd(srcBegin, srcEnd, length());
 checkBoundsOffCount(dstBegin, srcEnd - srcBegin, dst.length);
 if (isLatin1()) {
 StringLatin1.getChars(value, srcBegin, srcEnd, dst, dstBegin);
 } else {
 StringUTF16.getChars(value, srcBegin, srcEnd, dst, dstBegin);
 }
 }

 /**
 * Copies characters from this string into the destination byte array. Each
 * byte receives the 8 low-order bits of the corresponding character. The
 * eight high-order bits of each character are not copied and do not
 * participate in the transfer in any way.
 *
 * The first character to be copied is at index {@code srcBegin}; the
 * last character to be copied is at index {@code srcEnd-1}. The total
 * number of characters to be copied is {@code srcEnd-srcBegin}. The
 * characters, converted to bytes, are copied into the subarray of {@code
 * dst} starting at index {@code dstBegin} and ending at index:
 *
 * <blockquote><pre>
 * dstBegin + (srcEnd-srcBegin) - 1
 * </pre></blockquote>
 *
 * @deprecated This method does not properly convert characters into
 * bytes. As of JDK 1.1, the preferred way to do this is via the
 * {@link #getBytes()} method, which uses the {@link Charset#defaultCharset()
 * default charset}.
 *
 * @param srcBegin
 * Index of the first character in the string to copy
 *
 * @param srcEnd
 * Index after the last character in the string to copy
 *
 * @param dst
 * The destination array
 *
 * @param dstBegin
 * The start offset in the destination array
 *
 * @throws IndexOutOfBoundsException
 * If any of the following is true:
 * <ul>
 * <li> {@code srcBegin} is negative
 * <li> {@code srcBegin} is greater than {@code srcEnd}
 * <li> {@code srcEnd} is greater than the length of this String
 * <li> {@code dstBegin} is negative
 * <li> {@code dstBegin+(srcEnd-srcBegin)} is larger than {@code
 * dst.length}
 * </ul>
 */
 @Deprecated(since="1.1")
 public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) {
 checkBoundsBeginEnd(srcBegin, srcEnd, length());
 Objects.requireNonNull(dst);
 checkBoundsOffCount(dstBegin, srcEnd - srcBegin, dst.length);
 if (isLatin1()) {
 StringLatin1.getBytes(value, srcBegin, srcEnd, dst, dstBegin);
 } else {
 StringUTF16.getBytes(value, srcBegin, srcEnd, dst, dstBegin);
 }
 }

 /**
 * Encodes this {@code String} into a sequence of bytes using the named
 * charset, storing the result into a new byte array.
 *
 * The behavior of this method when this string cannot be encoded in
 * the given charset is unspecified. The {@link
 * java.nio.charset.CharsetEncoder} class should be used when more control
 * over the encoding process is required.
 *
 * @param charsetName
 * The name of a supported {@linkplain java.nio.charset.Charset
 * charset}
 *
 * @return The resultant byte array
 *
 * @throws UnsupportedEncodingException
 * If the named charset is not supported
 *
 * @since 1.1
 */
 public byte[] getBytes(String charsetName)
 throws UnsupportedEncodingException {
 return encode(lookupCharset(charsetName), coder(), value);
 }

 /**
 * Encodes this {@code String} into a sequence of bytes using the given
 * {@linkplain java.nio.charset.Charset charset}, storing the result into a
 * new byte array.
 *
 * This method always replaces malformed-input and unmappable-character
 * sequences with this charset's default replacement byte array. The
 * {@link java.nio.charset.CharsetEncoder} class should be used when more
 * control over the encoding process is required.
 *
 * @param charset
 * The {@linkplain java.nio.charset.Charset} to be used to encode
 * the {@code String}
 *
 * @return The resultant byte array
 *
 * @since 1.6
 */
 public byte[] getBytes(Charset charset) {
 if (charset == null) throw new NullPointerException();
 return encode(charset, coder(), value);
 }

 /**
 * Encodes this {@code String} into a sequence of bytes using the
 * {@link Charset#defaultCharset() default charset}, storing the result
 * into a new byte array.
 *
 * The behavior of this method when this string cannot be encoded in
 * the default charset is unspecified. The {@link
 * java.nio.charset.CharsetEncoder} class should be used when more control
 * over the encoding process is required.
 *
 * @return The resultant byte array
 *
 * @since 1.1
 */
 public byte[] getBytes() {
 return encode(Charset.defaultCharset(), coder(), value);
 }

 /**
 * Compares this string to the specified object. The result is {@code
 * true} if and only if the argument is not {@code null} and is a {@code
 * String} object that represents the same sequence of characters as this
 * object.
 *
 * For finer-grained String comparison, refer to
 * {@link java.text.Collator}.
 *
 * @param anObject
 * The object to compare this {@code String} against
 *
 * @return {@code true} if the given object represents a {@code String}
 * equivalent to this string, {@code false} otherwise
 *
 * @see #compareTo(String)
 * @see #equalsIgnoreCase(String)
 */
 public boolean equals(Object anObject) {
 if (this == anObject) {
 return true;
 }
 return (anObject instanceof String aString)
 && (!COMPACT_STRINGS || this.coder == aString.coder)
 && StringLatin1.equals(value, aString.value);
 }

 /**
 * Compares this string to the specified {@code StringBuffer}. The result
 * is {@code true} if and only if this {@code String} represents the same
 * sequence of characters as the specified {@code StringBuffer}. This method
 * synchronizes on the {@code StringBuffer}.
 *
 * For finer-grained String comparison, refer to
 * {@link java.text.Collator}.
 *
 * @param sb
 * The {@code StringBuffer} to compare this {@code String} against
 *
 * @return {@code true} if this {@code String} represents the same
 * sequence of characters as the specified {@code StringBuffer},
 * {@code false} otherwise
 *
 * @since 1.4
 */
 public boolean contentEquals(StringBuffer sb) {
 return contentEquals((CharSequence)sb);
 }

 private boolean nonSyncContentEquals(AbstractStringBuilder sb) {
 int len = length();
 if (len != sb.length()) {
 return false;
 }
 byte v1[] = value;
 byte v2[] = sb.getValue();
 byte coder = coder();
 if (coder == sb.getCoder()) {
 int n = v1.length;
 for (int i = 0; i < n; i++) {
 if (v1[i] != v2[i]) {
 return false;
 }
 }
 } else {
 if (coder != LATIN1) { // utf16 str and latin1 abs can never be "equal"
 return false;
 }
 return StringUTF16.contentEquals(v1, v2, len);
 }
 return true;
 }

 /**
 * Compares this string to the specified {@code CharSequence}. The
 * result is {@code true} if and only if this {@code String} represents the
 * same sequence of char values as the specified sequence. Note that if the
 * {@code CharSequence} is a {@code StringBuffer} then the method
 * synchronizes on it.
 *
 * For finer-grained String comparison, refer to
 * {@link java.text.Collator}.
 *
 * @param cs
 * The sequence to compare this {@code String} against
 *
 * @return {@code true} if this {@code String} represents the same
 * sequence of char values as the specified sequence, {@code
 * false} otherwise
 *
 * @since 1.5
 */
 public boolean contentEquals(CharSequence cs) {
 // Argument is a StringBuffer, StringBuilder
 if (cs instanceof AbstractStringBuilder) {
 if (cs instanceof StringBuffer) {
 synchronized(cs) {
 return nonSyncContentEquals((AbstractStringBuilder)cs);
 }
 } else {
 return nonSyncContentEquals((AbstractStringBuilder)cs);
 }
 }
 // Argument is a String
 if (cs instanceof String) {
 return equals(cs);
 }
 // Argument is a generic CharSequence
 int n = cs.length();
 if (n != length()) {
 return false;
 }
 byte[] val = this.value;
 if (isLatin1()) {
 for (int i = 0; i < n; i++) {
 if ((val[i] & 0xff) != cs.charAt(i)) {
 return false;
 }
 }
 } else {
 if (!StringUTF16.contentEquals(val, cs, n)) {
 return false;
 }
 }
 return true;
 }

 /**
 * Compares this {@code String} to another {@code String}, ignoring case
 * considerations. Two strings are considered equal ignoring case if they
 * are of the same length and corresponding Unicode code points in the two
 * strings are equal ignoring case.
 *
 * Two Unicode code points are considered the same
 * ignoring case if at least one of the following is true:
 * <ul>
 * <li> The two Unicode code points are the same (as compared by the
 * {@code ==} operator)
 * <li> Calling {@code Character.toLowerCase(Character.toUpperCase(int))}
 * on each Unicode code point produces the same result
 * </ul>
 *
 * Note that this method does not take locale into account, and
 * will result in unsatisfactory results for certain locales. The
 * {@link java.text.Collator} class provides locale-sensitive comparison.
 *
 * @param anotherString
 * The {@code String} to compare this {@code String} against
 *
 * @return {@code true} if the argument is not {@code null} and it
 * represents an equivalent {@code String} ignoring case; {@code
 * false} otherwise
 *
 * @see #equals(Object)
 * @see #codePoints()
 */
 public boolean equalsIgnoreCase(String anotherString) {
 return (this == anotherString) ? true
 : (anotherString != null)
 && (anotherString.length() == length())
 && regionMatches(true, 0, anotherString, 0, length());
 }

 /**
 * Compares two strings lexicographically.
 * The comparison is based on the Unicode value of each character in
 * the strings. The character sequence represented by this
 * {@code String} object is compared lexicographically to the
 * character sequence represented by the argument string. The result is
 * a negative integer if this {@code String} object
 * lexicographically precedes the argument string. The result is a
 * positive integer if this {@code String} object lexicographically
 * follows the argument string. The result is zero if the strings
 * are equal; {@code compareTo} returns {@code 0} exactly when
 * the {@link #equals(Object)} method would return {@code true}.
 * 
 * This is the definition of lexicographic ordering. If two strings are
 * different, then either they have different characters at some index
 * that is a valid index for both strings, or their lengths are different,
 * or both. If they have different characters at one or more index
 * positions, let k be the smallest such index; then the string
 * whose character at position k has the smaller value, as
 * determined by using the {@code <} operator, lexicographically precedes the
 * other string. In this case, {@code compareTo} returns the
 * difference of the two character values at position {@code k} in
 * the two string -- that is, the value:
 * <blockquote><pre>
 * this.charAt(k)-anotherString.charAt(k)
 * </pre></blockquote>
 * If there is no index position at which they differ, then the shorter
 * string lexicographically precedes the longer string. In this case,
 * {@code compareTo} returns the difference of the lengths of the
 * strings -- that is, the value:
 * <blockquote><pre>
 * this.length()-anotherString.length()
 * </pre></blockquote>
 *
 * For finer-grained String comparison, refer to
 * {@link java.text.Collator}.
 *
 * @param anotherString the {@code String} to be compared.
 * @return the value {@code 0} if the argument string is equal to
 * this string; a value less than {@code 0} if this string
 * is lexicographically less than the string argument; and a
 * value greater than {@code 0} if this string is
 * lexicographically greater than the string argument.
 */
 public int compareTo(String anotherString) {
 byte v1[] = value;
 byte v2[] = anotherString.value;
 byte coder = coder();
 if (coder == anotherString.coder()) {
 return coder == LATIN1 ? StringLatin1.compareTo(v1, v2)
 : StringUTF16.compareTo(v1, v2);
 }
 return coder == LATIN1 ? StringLatin1.compareToUTF16(v1, v2)
 : StringUTF16.compareToLatin1(v1, v2);
 }

 /**
 * A Comparator that orders {@code String} objects as by
 * {@link #compareToIgnoreCase(String) compareToIgnoreCase}.
 * This comparator is serializable.
 * 
 * Note that this Comparator does not take locale into account,
 * and will result in an unsatisfactory ordering for certain locales.
 * The {@link java.text.Collator} class provides locale-sensitive comparison.
 *
 * @see java.text.Collator
 * @since 1.2
 */
 public static final Comparator<String> CASE_INSENSITIVE_ORDER
 = new CaseInsensitiveComparator();

 /**
 * CaseInsensitiveComparator for Strings.
 */
 private static class CaseInsensitiveComparator
 implements Comparator<String>, java.io.Serializable {
 // use serialVersionUID from JDK 1.2.2 for interoperability
 @java.io.Serial
 private static final long serialVersionUID = 8575799808933029326L;

 public int compare(String s1, String s2) {
 byte v1[] = s1.value;
 byte v2[] = s2.value;
 byte coder = s1.coder();
 if (coder == s2.coder()) {
 return coder == LATIN1 ? StringLatin1.compareToCI(v1, v2)
 : StringUTF16.compareToCI(v1, v2);
 }
 return coder == LATIN1 ? StringLatin1.compareToCI_UTF16(v1, v2)
 : StringUTF16.compareToCI_Latin1(v1, v2);
 }

 /** Replaces the de-serialized object. */
 @java.io.Serial
 private Object readResolve() { return CASE_INSENSITIVE_ORDER; }
 }

 /**
 * Compares two strings lexicographically, ignoring case
 * differences. This method returns an integer whose sign is that of
 * calling {@code compareTo} with case folded versions of the strings
 * where case differences have been eliminated by calling
 * {@code Character.toLowerCase(Character.toUpperCase(int))} on
 * each Unicode code point.
 * 
 * Note that this method does not take locale into account,
 * and will result in an unsatisfactory ordering for certain locales.
 * The {@link java.text.Collator} class provides locale-sensitive comparison.
 *
 * @param str the {@code String} to be compared.
 * @return a negative integer, zero, or a positive integer as the
 * specified String is greater than, equal to, or less
 * than this String, ignoring case considerations.
 * @see java.text.Collator
 * @see #codePoints()
 * @since 1.2
 */
 public int compareToIgnoreCase(String str) {
 return CASE_INSENSITIVE_ORDER.compare(this, str);
 }

 /**
 * Tests if two string regions are equal.
 * 
 * A substring of this {@code String} object is compared to a substring
 * of the argument other. The result is true if these substrings
 * represent identical character sequences. The substring of this
 * {@code String} object to be compared begins at index {@code toffset}
 * and has length {@code len}. The substring of other to be compared
 * begins at index {@code ooffset} and has length {@code len}. The
 * result is {@code false} if and only if at least one of the following
 * is true:
 * <ul><li>{@code toffset} is negative.
 * <li>{@code ooffset} is negative.
 * <li>{@code toffset+len} is greater than the length of this
 * {@code String} object.
 * <li>{@code ooffset+len} is greater than the length of the other
 * argument.
 * <li>There is some nonnegative integer k less than {@code len}
 * such that:
 * {@code this.charAt(toffset + }k{@code ) != other.charAt(ooffset + }
 * k{@code )}
 * </ul>
 *
 * Note that this method does not take locale into account. The
 * {@link java.text.Collator} class provides locale-sensitive comparison.
 *
 * @param toffset the starting offset of the subregion in this string.
 * @param other the string argument.
 * @param ooffset the starting offset of the subregion in the string
 * argument.
 * @param len the number of characters to compare.
 * @return {@code true} if the specified subregion of this string
 * exactly matches the specified subregion of the string argument;
 * {@code false} otherwise.
 */
 public boolean regionMatches(int toffset, String other, int ooffset, int len) {
 byte tv[] = value;
 byte ov[] = other.value;
 // Note: toffset, ooffset, or len might be near -1>>>1.
 if ((ooffset < 0) || (toffset < 0) ||
 (toffset > (long)length() - len) ||
 (ooffset > (long)other.length() - len)) {
 return false;
 }
 byte coder = coder();
 if (coder == other.coder()) {
 if (!isLatin1() && (len > 0)) {
 toffset = toffset << 1;
 ooffset = ooffset << 1;
 len = len << 1;
 }
 while (len-- > 0) {
 if (tv[toffset++] != ov[ooffset++]) {
 return false;
 }
 }
 } else {
 if (coder == LATIN1) {
 while (len-- > 0) {
 if (StringLatin1.getChar(tv, toffset++) !=
 StringUTF16.getChar(ov, ooffset++)) {
 return false;
 }
 }
 } else {
 while (len-- > 0) {
 if (StringUTF16.getChar(tv, toffset++) !=
 StringLatin1.getChar(ov, ooffset++)) {
 return false;
 }
 }
 }
 }
 return true;
 }

 /**
 * Tests if two string regions are equal.
 * 
 * A substring of this {@code String} object is compared to a substring
 * of the argument {@code other}. The result is {@code true} if these
 * substrings represent Unicode code point sequences that are the same,
 * ignoring case if and only if {@code ignoreCase} is true.
 * The sequences {@code tsequence} and {@code osequence} are compared,
 * where {@code tsequence} is the sequence produced as if by calling
 * {@code this.substring(toffset, toffset + len).codePoints()} and
 * {@code osequence} is the sequence produced as if by calling
 * {@code other.substring(ooffset, ooffset + len).codePoints()}.
 * The result is {@code true} if and only if all of the following
 * are true:
 * <ul><li>{@code toffset} is non-negative.
 * <li>{@code ooffset} is non-negative.
 * <li>{@code toffset+len} is less than or equal to the length of this
 * {@code String} object.
 * <li>{@code ooffset+len} is less than or equal to the length of the other
 * argument.
 * <li>if {@code ignoreCase} is {@code false}, all pairs of corresponding Unicode
 * code points are equal integer values; or if {@code ignoreCase} is {@code true},
 * {@link Character#toLowerCase(int) Character.toLowerCase(}
 * {@link Character#toUpperCase(int)}{@code )} on all pairs of Unicode code points
 * results in equal integer values.
 * </ul>
 *
 * Note that this method does not take locale into account,
 * and will result in unsatisfactory results for certain locales when
 * {@code ignoreCase} is {@code true}. The {@link java.text.Collator} class
 * provides locale-sensitive comparison.
 *
 * @param ignoreCase if {@code true}, ignore case when comparing
 * characters.
 * @param toffset the starting offset of the subregion in this
 * string.
 * @param other the string argument.
 * @param ooffset the starting offset of the subregion in the string
 * argument.
 * @param len the number of characters (Unicode code units -
 * 16bit {@code char} value) to compare.
 * @return {@code true} if the specified subregion of this string
 * matches the specified subregion of the string argument;
 * {@code false} otherwise. Whether the matching is exact
 * or case insensitive depends on the {@code ignoreCase}
 * argument.
 * @see #codePoints()
 */
 public boolean regionMatches(boolean ignoreCase, int toffset,
 String other, int ooffset, int len) {
 if (!ignoreCase) {
 return regionMatches(toffset, other, ooffset, len);
 }
 // Note: toffset, ooffset, or len might be near -1>>>1.
 if ((ooffset < 0) || (toffset < 0)
 || (toffset > (long)length() - len)
 || (ooffset > (long)other.length() - len)) {
 return false;
 }
 byte tv[] = value;
 byte ov[] = other.value;
 byte coder = coder();
 if (coder == other.coder()) {
 return coder == LATIN1
 ? StringLatin1.regionMatchesCI(tv, toffset, ov, ooffset, len)
 : StringUTF16.regionMatchesCI(tv, toffset, ov, ooffset, len);
 }
 return coder == LATIN1
 ? StringLatin1.regionMatchesCI_UTF16(tv, toffset, ov, ooffset, len)
 : StringUTF16.regionMatchesCI_Latin1(tv, toffset, ov, ooffset, len);
 }

 /**
 * Tests if the substring of this string beginning at the
 * specified index starts with the specified prefix.
 *
 * @param prefix the prefix.
 * @param toffset where to begin looking in this string.
 * @return {@code true} if the character sequence represented by the
 * argument is a prefix of the substring of this object starting
 * at index {@code toffset}; {@code false} otherwise.
 * The result is {@code false} if {@code toffset} is
 * negative or greater than the length of this
 * {@code String} object; otherwise the result is the same
 * as the result of the expression
 * <pre>
 * this.substring(toffset).startsWith(prefix)
 * </pre>
 */
 public boolean startsWith(String prefix, int toffset) {
 // Note: toffset might be near -1>>>1.
 if (toffset < 0 || toffset > length() - prefix.length()) {
 return false;
 }
 byte ta[] = value;
 byte pa[] = prefix.value;
 int po = 0;
 int pc = pa.length;
 byte coder = coder();
 if (coder == prefix.coder()) {
 int to = (coder == LATIN1) ? toffset : toffset << 1;
 while (po < pc) {
 if (ta[to++] != pa[po++]) {
 return false;
 }
 }
 } else {
 if (coder == LATIN1) { // && pcoder == UTF16
 return false;
 }
 // coder == UTF16 && pcoder == LATIN1)
 while (po < pc) {
 if (StringUTF16.getChar(ta, toffset++) != (pa[po++] & 0xff)) {
 return false;
 }
 }
 }
 return true;
 }

 /**
 * Tests if this string starts with the specified prefix.
 *
 * @param prefix the prefix.
 * @return {@code true} if the character sequence represented by the
 * argument is a prefix of the character sequence represented by
 * this string; {@code false} otherwise.
 * Note also that {@code true} will be returned if the
 * argument is an empty string or is equal to this
 * {@code String} object as determined by the
 * {@link #equals(Object)} method.
 * @since 1.0
 */
 public boolean startsWith(String prefix) {
 return startsWith(prefix, 0);
 }

 /**
 * Tests if this string ends with the specified suffix.
 *
 * @param suffix the suffix.
 * @return {@code true} if the character sequence represented by the
 * argument is a suffix of the character sequence represented by
 * this object; {@code false} otherwise. Note that the
 * result will be {@code true} if the argument is the
 * empty string or is equal to this {@code String} object
 * as determined by the {@link #equals(Object)} method.
 */
 public boolean endsWith(String suffix) {
 return startsWith(suffix, length() - suffix.length());
 }

 /**
 * Returns a hash code for this string. The hash code for a
 * {@code String} object is computed as
 * <blockquote><pre>
 * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
 * </pre></blockquote>
 * using {@code int} arithmetic, where {@code s[i]} is the
 * ith character of the string, {@code n} is the length of
 * the string, and {@code ^} indicates exponentiation.
 * (The hash value of the empty string is zero.)
 *
 * @return a hash code value for this object.
 */
 public int hashCode() {
 // The hash or hashIsZero fields are subject to a benign data race,
 // making it crucial to ensure that any observable result of the
 // calculation in this method stays correct under any possible read of
 // these fields. Necessary restrictions to allow this to be correct
 // without explicit memory fences or similar concurrency primitives is
 // that we can ever only write to one of these two fields for a given
 // String instance, and that the computation is idempotent and derived
 // from immutable state
 int h = hash;
 if (h == 0 && !hashIsZero) {
 h = isLatin1() ? StringLatin1.hashCode(value)
 : StringUTF16.hashCode(value);
 if (h == 0) {
 hashIsZero = true;
 } else {
 hash = h;
 }
 }
 return h;
 }

 /**
 * Returns the index within this string of the first occurrence of
 * the specified character. If a character with value
 * {@code ch} occurs in the character sequence represented by
 * this {@code String} object, then the index (in Unicode
 * code units) of the first such occurrence is returned. For
 * values of {@code ch} in the range from 0 to 0xFFFF
 * (inclusive), this is the smallest value k such that:
 * <blockquote><pre>
 * this.charAt(k) == ch
 * </pre></blockquote>
 * is true. For other values of {@code ch}, it is the
 * smallest value k such that:
 * <blockquote><pre>
 * this.codePointAt(k) == ch
 * </pre></blockquote>
 * is true. In either case, if no such character occurs in this
 * string, then {@code -1} is returned.
 *
 * @param ch a character (Unicode code point).
 * @return the index of the first occurrence of the character in the
 * character sequence represented by this object, or
 * {@code -1} if the character does not occur.
 */
 public int indexOf(int ch) {
 return indexOf(ch, 0);
 }

 /**
 * Returns the index within this string of the first occurrence of the
 * specified character, starting the search at the specified index.
 * 
 * If a character with value {@code ch} occurs in the
 * character sequence represented by this {@code String}
 * object at an index no smaller than {@code fromIndex}, then
 * the index of the first such occurrence is returned. For values
 * of {@code ch} in the range from 0 to 0xFFFF (inclusive),
 * this is the smallest value k such that:
 * <blockquote><pre>
 * (this.charAt(k) == ch) {@code &&} (k >= fromIndex)
 * </pre></blockquote>
 * is true. For other values of {@code ch}, it is the
 * smallest value k such that:
 * <blockquote><pre>
 * (this.codePointAt(k) == ch) {@code &&} (k >= fromIndex)
 * </pre></blockquote>
 * is true. In either case, if no such character occurs in this
 * string at or after position {@code fromIndex}, then
 * {@code -1} is returned.
 *
 * 
 * There is no restriction on the value of {@code fromIndex}. If it
 * is negative, it has the same effect as if it were zero: this entire
 * string may be searched. If it is greater than the length of this
 * string, it has the same effect as if it were equal to the length of
 * this string: {@code -1} is returned.
 *
 * All indices are specified in {@code char} values
 * (Unicode code units).
 *
 * @param ch a character (Unicode code point).
 * @param fromIndex the index to start the search from.
 * @return the index of the first occurrence of the character in the
 * character sequence represented by this object that is greater
 * than or equal to {@code fromIndex}, or {@code -1}
 * if the character does not occur.
 */
 public int indexOf(int ch, int fromIndex) {
 return isLatin1() ? StringLatin1.indexOf(value, ch, fromIndex)
 : StringUTF16.indexOf(value, ch, fromIndex);
 }

 /**
 * Returns the index within this string of the last occurrence of
 * the specified character. For values of {@code ch} in the
 * range from 0 to 0xFFFF (inclusive), the index (in Unicode code
 * units) returned is the largest value k such that:
 * <blockquote><pre>
 * this.charAt(k) == ch
 * </pre></blockquote>
 * is true. For other values of {@code ch}, it is the
 * largest value k such that:
 * <blockquote><pre>
 * this.codePointAt(k) == ch
 * </pre></blockquote>
 * is true. In either case, if no such character occurs in this
 * string, then {@code -1} is returned. The
 * {@code String} is searched backwards starting at the last
 * character.
 *
 * @param ch a character (Unicode code point).
 * @return the index of the last occurrence of the character in the
 * character sequence represented by this object, or
 * {@code -1} if the character does not occur.
 */
 public int lastIndexOf(int ch) {
 return lastIndexOf(ch, length() - 1);
 }

 /**
 * Returns the index within this string of the last occurrence of
 * the specified character, searching backward starting at the
 * specified index. For values of {@code ch} in the range
 * from 0 to 0xFFFF (inclusive), the index returned is the largest
 * value k such that:
 * <blockquote><pre>
 * (this.charAt(k) == ch) {@code &&} (k <= fromIndex)
 * </pre></blockquote>
 * is true. For other values of {@code ch}, it is the
 * largest value k such that:
 * <blockquote><pre>
 * (this.codePointAt(k) == ch) {@code &&} (k <= fromIndex)
 * </pre></blockquote>
 * is true. In either case, if no such character occurs in this
 * string at or before position {@code fromIndex}, then
 * {@code -1} is returned.
 *
 * All indices are specified in {@code char} values
 * (Unicode code units).
 *
 * @param ch a character (Unicode code point).
 * @param fromIndex the index to start the search from. There is no
 * restriction on the value of {@code fromIndex}. If it is
 * greater than or equal to the length of this string, it has
 * the same effect as if it were equal to one less than the
 * length of this string: this entire string may be searched.
 * If it is negative, it has the same effect as if it were -1:
 * -1 is returned.
 * @return the index of the last occurrence of the character in the
 * character sequence represented by this object that is less
 * than or equal to {@code fromIndex}, or {@code -1}
 * if the character does not occur before that point.
 */
 public int lastIndexOf(int ch, int fromIndex) {
 return isLatin1() ? StringLatin1.lastIndexOf(value, ch, fromIndex)
 : StringUTF16.lastIndexOf(value, ch, fromIndex);
 }

 /**
 * Returns the index within this string of the first occurrence of the
 * specified substring.
 *
 * The returned index is the smallest value {@code k} for which:
 * <pre>{@code
 * this.startsWith(str, k)
 * }</pre>
 * If no such value of {@code k} exists, then {@code -1} is returned.
 *
 * @param str the substring to search for.
 * @return the index of the first occurrence of the specified substring,
 * or {@code -1} if there is no such occurrence.
 */
 public int indexOf(String str) {
 byte coder = coder();
 if (coder == str.coder()) {
 return isLatin1() ? StringLatin1.indexOf(value, str.value)
 : StringUTF16.indexOf(value, str.value);
 }
 if (coder == LATIN1) { // str.coder == UTF16
 return -1;
 }
 return StringUTF16.indexOfLatin1(value, str.value);
 }

 /**
 * Returns the index within this string of the first occurrence of the
 * specified substring, starting at the specified index.
 *
 * The returned index is the smallest value {@code k} for which:
 * <pre>{@code
 * k >= Math.min(fromIndex, this.length()) &&
 * this.startsWith(str, k)
 * }</pre>
 * If no such value of {@code k} exists, then {@code -1} is returned.
 *
 * @param str the substring to search for.
 * @param fromIndex the index from which to start the search.
 * @return the index of the first occurrence of the specified substring,
 * starting at the specified index,
 * or {@code -1} if there is no such occurrence.
 */
 public int indexOf(String str, int fromIndex) {
 return indexOf(value, coder(), length(), str, fromIndex);
 }

 /**
 * Code shared by String and AbstractStringBuilder to do searches. The
 * source is the character array being searched, and the target
 * is the string being searched for.
 *
 * @param src the characters being searched.
 * @param srcCoder the coder of the source string.
 * @param srcCount length of the source string.
 * @param tgtStr the characters being searched for.
 * @param fromIndex the index to begin searching from.
 */
 static int indexOf(byte[] src, byte srcCoder, int srcCount,
 String tgtStr, int fromIndex) {
 byte[] tgt = tgtStr.value;
 byte tgtCoder = tgtStr.coder();
 int tgtCount = tgtStr.length();

 if (fromIndex >= srcCount) {
 return (tgtCount == 0 ? srcCount : -1);
 }
 if (fromIndex < 0) {
 fromIndex = 0;
 }
 if (tgtCount == 0) {
 return fromIndex;
 }
 if (tgtCount > srcCount) {
 return -1;
 }
 if (srcCoder == tgtCoder) {
 return srcCoder == LATIN1
 ? StringLatin1.indexOf(src, srcCount, tgt, tgtCount, fromIndex)
 : StringUTF16.indexOf(src, srcCount, tgt, tgtCount, fromIndex);
 }
 if (srcCoder == LATIN1) { // && tgtCoder == UTF16
 return -1;
 }
 // srcCoder == UTF16 && tgtCoder == LATIN1) {
 return StringUTF16.indexOfLatin1(src, srcCount, tgt, tgtCount, fromIndex);
 }

 /**
 * Returns the index within this string of the last occurrence of the
 * specified substring. The last occurrence of the empty string ""
 * is considered to occur at the index value {@code this.length()}.
 *
 * The returned index is the largest value {@code k} for which:
 * <pre>{@code
 * this.startsWith(str, k)
 * }</pre>
 * If no such value of {@code k} exists, then {@code -1} is returned.
 *
 * @param str the substring to search for.
 * @return the index of the last occurrence of the specified substring,
 * or {@code -1} if there is no such occurrence.
 */
 public int lastIndexOf(String str) {
 return lastIndexOf(str, length());
 }

 /**
 * Returns the index within this string of the last occurrence of the
 * specified substring, searching backward starting at the specified index.
 *
 * The returned index is the largest value {@code k} for which:
 * <pre>{@code
 * k <= Math.min(fromIndex, this.length()) &&
 * this.startsWith(str, k)
 * }</pre>
 * If no such value of {@code k} exists, then {@code -1} is returned.
 *
 * @param str the substring to search for.
 * @param fromIndex the index to start the search from.
 * @return the index of the last occurrence of the specified substring,
 * searching backward from the specified index,
 * or {@code -1} if there is no such occurrence.
 */
 public int lastIndexOf(String str, int fromIndex) {
 return lastIndexOf(value, coder(), length(), str, fromIndex);
 }

 /**
 * Code shared by String and AbstractStringBuilder to do searches. The
 * source is the character array being searched, and the target
 * is the string being searched for.
 *
 * @param src the characters being searched.
 * @param srcCoder coder handles the mapping between bytes/chars
 * @param srcCount count of the source string.
 * @param tgtStr the characters being searched for.
 * @param fromIndex the index to begin searching from.
 */
 static int lastIndexOf(byte[] src, byte srcCoder, int srcCount,
 String tgtStr, int fromIndex) {
 byte[] tgt = tgtStr.value;
 byte tgtCoder = tgtStr.coder();
 int tgtCount = tgtStr.length();
 /*
 * Check arguments; return immediately where possible. For
 * consistency, don't check for null str.
 */
 int rightIndex = srcCount - tgtCount;
 if (fromIndex > rightIndex) {
 fromIndex = rightIndex;
 }
 if (fromIndex < 0) {
 return -1;
 }
 /* Empty string always matches. */
 if (tgtCount == 0) {
 return fromIndex;
 }
 if (srcCoder == tgtCoder) {
 return srcCoder == LATIN1
 ? StringLatin1.lastIndexOf(src, srcCount, tgt, tgtCount, fromIndex)
 : StringUTF16.lastIndexOf(src, srcCount, tgt, tgtCount, fromIndex);
 }
 if (srcCoder == LATIN1) { // && tgtCoder == UTF16
 return -1;
 }
 // srcCoder == UTF16 && tgtCoder == LATIN1
 return StringUTF16.lastIndexOfLatin1(src, srcCount, tgt, tgtCount, fromIndex);
 }

 /**
 * Returns a string that is a substring of this string. The
 * substring begins with the character at the specified index and
 * extends to the end of this string. 
 * Examples:
 * <blockquote><pre>
 * "unhappy".substring(2) returns "happy"
 * "Harbison".substring(3) returns "bison"
 * "emptiness".substring(9) returns "" (an empty string)
 * </pre></blockquote>
 *
 * @param beginIndex the beginning index, inclusive.
 * @return the specified substring.
 * @throws IndexOutOfBoundsException if
 * {@code beginIndex} is negative or larger than the
 * length of this {@code String} object.
 */
 public String substring(int beginIndex) {
 return substring(beginIndex, length());
 }

 /**
 * Returns a string that is a substring of this string. The
 * substring begins at the specified {@code beginIndex} and
 * extends to the character at index {@code endIndex - 1}.
 * Thus the length of the substring is {@code endIndex-beginIndex}.
 * 
 * Examples:
 * <blockquote><pre>
 * "hamburger".substring(4, 8) returns "urge"
 * "smiles".substring(1, 5) returns "mile"
 * </pre></blockquote>
 *
 * @param beginIndex the beginning index, inclusive.
 * @param endIndex the ending index, exclusive.
 * @return the specified substring.
 * @throws IndexOutOfBoundsException if the
 * {@code beginIndex} is negative, or
 * {@code endIndex} is larger than the length of
 * this {@code String} object, or
 * {@code beginIndex} is larger than
 * {@code endIndex}.
 */
 public String substring(int beginIndex, int endIndex) {
 int length = length();
 checkBoundsBeginEnd(beginIndex, endIndex, length);
 if (beginIndex == 0 && endIndex == length) {
 return this;
 }
 int subLen = endIndex - beginIndex;
 return isLatin1() ? StringLatin1.newString(value, beginIndex, subLen)
 : StringUTF16.newString(value, beginIndex, subLen);
 }

 /**
 * Returns a character sequence that is a subsequence of this sequence.
 *
 * An invocation of this method of the form
 *
 * <blockquote><pre>
 * str.subSequence(begin, end)</pre></blockquote>
 *
 * behaves in exactly the same way as the invocation
 *
 * <blockquote><pre>
 * str.substring(begin, end)</pre></blockquote>
 *
 * @apiNote
 * This method is defined so that the {@code String} class can implement
 * the {@link CharSequence} interface.
 *
 * @param beginIndex the begin index, inclusive.
 * @param endIndex the end index, exclusive.
 * @return the specified subsequence.
 *
 * @throws IndexOutOfBoundsException
 * if {@code beginIndex} or {@code endIndex} is negative,
 * if {@code endIndex} is greater than {@code length()},
 * or if {@code beginIndex} is greater than {@code endIndex}
 *
 * @since 1.4
 */
 public CharSequence subSequence(int beginIndex, int endIndex) {
 return this.substring(beginIndex, endIndex);
 }

 /**
 * Concatenates the specified string to the end of this string.
 * 
 * If the length of the argument string is {@code 0}, then this
 * {@code String} object is returned. Otherwise, a
 * {@code String} object is returned that represents a character
 * sequence that is the concatenation of the character sequence
 * represented by this {@code String} object and the character
 * sequence represented by the argument string.
 * Examples:
 * <blockquote><pre>
 * "cares".concat("s") returns "caress"
 * "to".concat("get").concat("her") returns "together"
 * </pre></blockquote>
 *
 * @param str the {@code String} that is concatenated to the end
 * of this {@code String}.
 * @return a string that represents the concatenation of this object's
 * characters followed by the string argument's characters.
 */
 public String concat(String str) {
 if (str.isEmpty()) {
 return this;
 }
 return StringConcatHelper.simpleConcat(this, str);
 }

 /**
 * Returns a string resulting from replacing all occurrences of
 * {@code oldChar} in this string with {@code newChar}.
 * 
 * If the character {@code oldChar} does not occur in the
 * character sequence represented by this {@code String} object,
 * then a reference to this {@code String} object is returned.
 * Otherwise, a {@code String} object is returned that
 * represents a character sequence identical to the character sequence
 * represented by this {@code String} object, except that every
 * occurrence of {@code oldChar} is replaced by an occurrence
 * of {@code newChar}.
 * 
 * Examples:
 * <blockquote><pre>
 * "mesquite in your cellar".replace('e', 'o')
 * returns "mosquito in your collar"
 * "the war of baronets".replace('r', 'y')
 * returns "the way of bayonets"
 * "sparring with a purple porpoise".replace('p', 't')
 * returns "starring with a turtle tortoise"
 * "JonL".replace('q', 'x') returns "JonL" (no change)
 * </pre></blockquote>
 *
 * @param oldChar the old character.
 * @param newChar the new character.
 * @return a string derived from this string by replacing every
 * occurrence of {@code oldChar} with {@code newChar}.
 */
 public String replace(char oldChar, char newChar) {
 if (oldChar != newChar) {
 String ret = isLatin1() ? StringLatin1.replace(value, oldChar, newChar)
 : StringUTF16.replace(value, oldChar, newChar);
 if (ret != null) {
 return ret;
 }
 }
 return this;
 }

 /**
 * Tells whether or not this string matches the given <a
 * href="../util/regex/Pattern.html#sum">regular expression</a>.
 *
 * An invocation of this method of the form
 * str{@code .matches(}regex{@code )} yields exactly the
 * same result as the expression
 *
 * <blockquote>
 * {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#matches(String,CharSequence)
 * matches(regex, str)}
 * </blockquote>
 *
 * @param regex
 * the regular expression to which this string is to be matched
 *
 * @return {@code true} if, and only if, this string matches the
 * given regular expression
 *
 * @throws PatternSyntaxException
 * if the regular expression's syntax is invalid
 *
 * @see java.util.regex.Pattern
 *
 * @since 1.4
 */
 public boolean matches(String regex) {
 return Pattern.matches(regex, this);
 }

 /**
 * Returns true if and only if this string contains the specified
 * sequence of char values.
 *
 * @param s the sequence to search for
 * @return true if this string contains {@code s}, false otherwise
 * @since 1.5
 */
 public boolean contains(CharSequence s) {
 return indexOf(s.toString()) >= 0;
 }

 /**
 * Replaces the first substring of this string that matches the given <a
 * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 * given replacement.
 *
 * An invocation of this method of the form
 * str{@code .replaceFirst(}regex{@code ,} repl{@code )}
 * yields exactly the same result as the expression
 *
 * <blockquote>
 * <code>
 * {@link java.util.regex.Pattern}.{@link
 * java.util.regex.Pattern#compile(String) compile}(regex).{@link
 * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(str).{@link
 * java.util.regex.Matcher#replaceFirst(String) replaceFirst}(repl)
 * </code>
 * </blockquote>
 *
 *
 * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
 * replacement string may cause the results to be different than if it were
 * being treated as a literal replacement string; see
 * {@link java.util.regex.Matcher#replaceFirst}.
 * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
 * meaning of these characters, if desired.
 *
 * @param regex
 * the regular expression to which this string is to be matched
 * @param replacement
 * the string to be substituted for the first match
 *
 * @return The resulting {@code String}
 *
 * @throws PatternSyntaxException
 * if the regular expression's syntax is invalid
 *
 * @see java.util.regex.Pattern
 *
 * @since 1.4
 */
 public String replaceFirst(String regex, String replacement) {
 return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
 }

 /**
 * Replaces each substring of this string that matches the given <a
 * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 * given replacement.
 *
 * An invocation of this method of the form
 * str{@code .replaceAll(}regex{@code ,} repl{@code )}
 * yields exactly the same result as the expression
 *
 * <blockquote>
 * <code>
 * {@link java.util.regex.Pattern}.{@link
 * java.util.regex.Pattern#compile(String) compile}(regex).{@link
 * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(str).{@link
 * java.util.regex.Matcher#replaceAll(String) replaceAll}(repl)
 * </code>
 * </blockquote>
 *
 *
 * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
 * replacement string may cause the results to be different than if it were
 * being treated as a literal replacement string; see
 * {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
 * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
 * meaning of these characters, if desired.
 *
 * @param regex
 * the regular expression to which this string is to be matched
 * @param replacement
 * the string to be substituted for each match
 *
 * @return The resulting {@code String}
 *
 * @throws PatternSyntaxException
 * if the regular expression's syntax is invalid
 *
 * @see java.util.regex.Pattern
 *
 * @since 1.4
 */
 public String replaceAll(String regex, String replacement) {
 return Pattern.compile(regex).matcher(this).replaceAll(replacement);
 }

 /**
 * Replaces each substring of this string that matches the literal target
 * sequence with the specified literal replacement sequence. The
 * replacement proceeds from the beginning of the string to the end, for
 * example, replacing "aa" with "b" in the string "aaa" will result in
 * "ba" rather than "ab".
 *
 * @param target The sequence of char values to be replaced
 * @param replacement The replacement sequence of char values
 * @return The resulting string
 * @since 1.5
 */
 public String replace(CharSequence target, CharSequence replacement) {
 String trgtStr = target.toString();
 String replStr = replacement.toString();
 int thisLen = length();
 int trgtLen = trgtStr.length();
 int replLen = replStr.length();

 if (trgtLen > 0) {
 if (trgtLen == 1 && replLen == 1) {
 return replace(trgtStr.charAt(0), replStr.charAt(0));
 }

 boolean thisIsLatin1 = this.isLatin1();
 boolean trgtIsLatin1 = trgtStr.isLatin1();
 boolean replIsLatin1 = replStr.isLatin1();
 String ret = (thisIsLatin1 && trgtIsLatin1 && replIsLatin1)
 ? StringLatin1.replace(value, thisLen,
 trgtStr.value, trgtLen,
 replStr.value, replLen)
 : StringUTF16.replace(value, thisLen, thisIsLatin1,
 trgtStr.value, trgtLen, trgtIsLatin1,
 replStr.value, replLen, replIsLatin1);
 if (ret != null) {
 return ret;
 }
 return this;

 } else { // trgtLen == 0
 int resultLen;
 try {
 resultLen = Math.addExact(thisLen, Math.multiplyExact(
 Math.addExact(thisLen, 1), replLen));
 } catch (ArithmeticException ignored) {
 throw new OutOfMemoryError("Required length exceeds implementation limit");
 }

 StringBuilder sb = new StringBuilder(resultLen);
 sb.append(replStr);
 for (int i = 0; i < thisLen; ++i) {
 sb.append(charAt(i)).append(replStr);
 }
 return sb.toString();
 }
 }

 /**
 * Splits this string around matches of the given
 * <a href="../util/regex/Pattern.html#sum">regular expression</a>.
 *
 * The array returned by this method contains each substring of this
 * string that is terminated by another substring that matches the given
 * expression or is terminated by the end of the string. The substrings in
 * the array are in the order in which they occur in this string. If the
 * expression does not match any part of the input then the resulting array
 * has just one element, namely this string.
 *
 * When there is a positive-width match at the beginning of this
 * string then an empty leading substring is included at the beginning
 * of the resulting array. A zero-width match at the beginning however
 * never produces such empty leading substring.
 *
 * The {@code limit} parameter controls the number of times the
 * pattern is applied and therefore affects the length of the resulting
 * array.
 * <ul>
 * <li>
 * If the limit is positive then the pattern will be applied
 * at most limit - 1 times, the array's length will be
 * no greater than limit, and the array's last entry will contain
 * all input beyond the last matched delimiter.</li>
 *
 * <li>
 * If the limit is zero then the pattern will be applied as
 * many times as possible, the array can have any length, and trailing
 * empty strings will be discarded.</li>
 *
 * <li>
 * If the limit is negative then the pattern will be applied
 * as many times as possible and the array can have any length.</li>
 * </ul>
 *
 * The string {@code "boo:and:foo"}, for example, yields the
 * following results with these parameters:
 *
 * <blockquote><table class="plain">
 * <caption style="display:none">Split example showing regex, limit, and result</caption>
 * <thead>
 * <tr>
 * <th scope="col">Regex</th>
 * <th scope="col">Limit</th>
 * <th scope="col">Result</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr><th scope="row" rowspan="3" style="font-weight:normal">:</th>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">2</th>
 * <td>{@code { "boo", "and:foo" }}</td></tr>
 * <tr>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
 * <td>{@code { "boo", "and", "foo" }}</td></tr>
 * <tr>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
 * <td>{@code { "boo", "and", "foo" }}</td></tr>
 * <tr><th scope="row" rowspan="3" style="font-weight:normal">o</th>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
 * <tr>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
 * <tr>
 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
 * <td>{@code { "b", "", ":and:f" }}</td></tr>
 * </tbody>
 * </table></blockquote>
 *
 * An invocation of this method of the form
 * str.{@code split(}regex{@code ,} n{@code )}
 * yields the same result as the expression
 *
 * <blockquote>
 * <code>
 * {@link java.util.regex.Pattern}.{@link
 * java.util.regex.Pattern#compile(String) compile}(regex).{@link
 * java.util.regex.Pattern#split(java.lang.CharSequence,int) split}(str, n)
 * </code>
 * </blockquote>
 *
 *
 * @param regex
 * the delimiting regular expression
 *
 * @param limit
 * the result threshold, as described above
 *
 * @return the array of strings computed by splitting this string
 * around matches of the given regular expression
 *
 * @throws PatternSyntaxException
 * if the regular expression's syntax is invalid
 *
 * @see java.util.regex.Pattern
 *
 * @since 1.4
 */
 public String[] split(String regex, int limit) {
 /* fastpath if the regex is a
 * (1) one-char String and this character is not one of the
 * RegEx's meta characters ".$|()[{^?*+\\", or
 * (2) two-char String and the first char is the backslash and
 * the second is not the ascii digit or ascii letter.
 */
 char ch = 0;
 if (((regex.length() == 1 &&
 ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||
 (regex.length() == 2 &&
 regex.charAt(0) == '\\' &&
 (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
 ((ch-'a')|('z'-ch)) < 0 &&
 ((ch-'A')|('Z'-ch)) < 0)) &&
 (ch < Character.MIN_HIGH_SURROGATE ||
 ch > Character.MAX_LOW_SURROGATE))
 {
 int off = 0;
 int next = 0;
 boolean limited = limit > 0;
 ArrayList<String> list = new ArrayList<>();
 while ((next = indexOf(ch, off)) != -1) {
 if (!limited || list.size() < limit - 1) {
 list.add(substring(off, next));
 off = next + 1;
 } else { // last one
 //assert (list.size() == limit - 1);
 int last = length();
 list.add(substring(off, last));
 off = last;
 break;
 }
 }
 // If no match was found, return this
 if (off == 0)
 return new String[]{this};

 // Add remaining segment
 if (!limited || list.size() < limit)
 list.add(substring(off, length()));

 // Construct result
 int resultSize = list.size();
 if (limit == 0) {
 while (resultSize > 0 && list.get(resultSize - 1).isEmpty()) {
 resultSize--;
 }
 }
 String[] result = new String[resultSize];
 return list.subList(0, resultSize).toArray(result);
 }
 return Pattern.compile(regex).split(this, limit);
 }

 /**
 * Splits this string around matches of the given <a
 * href="../util/regex/Pattern.html#sum">regular expression</a>.
 *
 * This method works as if by invoking the two-argument {@link
 * #split(String, int) split} method with the given expression and a limit
 * argument of zero. Trailing empty strings are therefore not included in
 * the resulting array.
 *
 * The string {@code "boo:and:foo"}, for example, yields the following
 * results with these expressions:
 *
 * <blockquote><table class="plain">
 * <caption style="display:none">Split examples showing regex and result</caption>
 * <thead>
 * <tr>
 * <th scope="col">Regex</th>
 * <th scope="col">Result</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr><th scope="row" style="text-weight:normal">:</th>
 * <td>{@code { "boo", "and", "foo" }}</td></tr>
 * <tr><th scope="row" style="text-weight:normal">o</th>
 * <td>{@code { "b", "", ":and:f" }}</td></tr>
 * </tbody>
 * </table></blockquote>
 *
 *
 * @param regex
 * the delimiting regular expression
 *
 * @return the array of strings computed by splitting this string
 * around matches of the given regular expression
 *
 * @throws PatternSyntaxException
 * if the regular expression's syntax is invalid
 *
 * @see java.util.regex.Pattern
 *
 * @since 1.4
 */
 public String[] split(String regex) {
 return split(regex, 0);
 }

 /**
 * Returns a new String composed of copies of the
 * {@code CharSequence elements} joined together with a copy of
 * the specified {@code delimiter}.
 *
 * <blockquote>For example,
 * <pre>{@code
 * String message = String.join("-", "Java", "is", "cool");
 * // message returned is: "Java-is-cool"
 * }</pre></blockquote>
 *
 * Note that if an element is null, then {@code "null"} is added.
 *
 * @param delimiter the delimiter that separates each element
 * @param elements the elements to join together.
 *
 * @return a new {@code String} that is composed of the {@code elements}
 * separated by the {@code delimiter}
 *
 * @throws NullPointerException If {@code delimiter} or {@code elements}
 * is {@code null}
 *
 * @see java.util.StringJoiner
 * @since 1.8
 */
 public static String join(CharSequence delimiter, CharSequence... elements) {
 var delim = delimiter.toString();
 var elems = new String[elements.length];
 for (int i = 0; i < elements.length; i++) {
 elems[i] = String.valueOf(elements[i]);
 }
 return join("", "", delim, elems, elems.length);
 }

 /**
 * Designated join routine.
 *
 * @param prefix the non-null prefix
 * @param suffix the non-null suffix
 * @param delimiter the non-null delimiter
 * @param elements the non-null array of non-null elements
 * @param size the number of elements in the array (<= elements.length)
 * @return the joined string
 */
 @ForceInline
 static String join(String prefix, String suffix, String delimiter, String[] elements, int size) {
 int icoder = prefix.coder() | suffix.coder();
 long len = (long) prefix.length() + suffix.length();
 if (size > 1) { // when there are more than one element, size - 1 delimiters will be emitted
 len += (long) (size - 1) * delimiter.length();
 icoder |= delimiter.coder();
 }
 // assert len > 0L; // max: (long) Integer.MAX_VALUE << 32
 // following loop will add max: (long) Integer.MAX_VALUE * Integer.MAX_VALUE to len
 // so len can overflow at most once
 for (int i = 0; i < size; i++) {
 var el = elements[i];
 len += el.length();
 icoder |= el.coder();
 }
 byte coder = (byte) icoder;
 // long len overflow check, char -> byte length, int len overflow check
 if (len < 0L || (len <<= coder) != (int) len) {
 throw new OutOfMemoryError("Requested string length exceeds VM limit");
 }
 byte[] value = StringConcatHelper.newArray(len);

 int off = 0;
 prefix.getBytes(value, off, coder); off += prefix.length();
 if (size > 0) {
 var el = elements[0];
 el.getBytes(value, off, coder); off += el.length();
 for (int i = 1; i < size; i++) {
 delimiter.getBytes(value, off, coder); off += delimiter.length();
 el = elements[i];
 el.getBytes(value, off, coder); off += el.length();
 }
 }
 suffix.getBytes(value, off, coder);
 // assert off + suffix.length() == value.length >> coder;

 return new String(value, coder);
 }

 /**
 * Returns a new {@code String} composed of copies of the
 * {@code CharSequence elements} joined together with a copy of the
 * specified {@code delimiter}.
 *
 * <blockquote>For example,
 * <pre>{@code
 * List<String> strings = List.of("Java", "is", "cool");
 * String message = String.join(" ", strings);
 * // message returned is: "Java is cool"
 *
 * Set<String> strings =
 * new LinkedHashSet<>(List.of("Java", "is", "very", "cool"));
 * String message = String.join("-", strings);
 * // message returned is: "Java-is-very-cool"
 * }</pre></blockquote>
 *
 * Note that if an individual element is {@code null}, then {@code "null"} is added.
 *
 * @param delimiter a sequence of characters that is used to separate each
 * of the {@code elements} in the resulting {@code String}
 * @param elements an {@code Iterable} that will have its {@code elements}
 * joined together.
 *
 * @return a new {@code String} that is composed from the {@code elements}
 * argument
 *
 * @throws NullPointerException If {@code delimiter} or {@code elements}
 * is {@code null}
 *
 * @see #join(CharSequence,CharSequence...)
 * @see java.util.StringJoiner
 * @since 1.8
 */
 public static String join(CharSequence delimiter,
 Iterable<? extends CharSequence> elements) {
 Objects.requireNonNull(delimiter);
 Objects.requireNonNull(elements);
 var delim = delimiter.toString();
 var elems = new String[8];
 int size = 0;
 for (CharSequence cs: elements) {
 if (size >= elems.length) {
 elems = Arrays.copyOf(elems, elems.length << 1);
 }
 elems[size++] = String.valueOf(cs);
 }
 return join("", "", delim, elems, size);
 }

 /**
 * Converts all of the characters in this {@code String} to lower
 * case using the rules of the given {@code Locale}. Case mapping is based
 * on the Unicode Standard version specified by the {@link java.lang.Character Character}
 * class. Since case mappings are not always 1:1 char mappings, the resulting {@code String}
 * and this {@code String} may differ in length.
 * 
 * Examples of lowercase mappings are in the following table:
 * <table class="plain">
 * <caption style="display:none">Lowercase mapping examples showing language code of locale, upper case, lower case, and description</caption>
 * <thead>
 * <tr>
 * <th scope="col">Language Code of Locale</th>
 * <th scope="col">Upper Case</th>
 * <th scope="col">Lower Case</th>
 * <th scope="col">Description</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr>
 * <td>tr (Turkish)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">\u0130</th>
 * <td>\u0069</td>
 * <td>capital letter I with dot above -> small letter i</td>
 * </tr>
 * <tr>
 * <td>tr (Turkish)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">\u0049</th>
 * <td>\u0131</td>
 * <td>capital letter I -> small letter dotless i </td>
 * </tr>
 * <tr>
 * <td>(all)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">French Fries</th>
 * <td>french fries</td>
 * <td>lowercased all chars in String</td>
 * </tr>
 * <tr>
 * <td>(all)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">
 * ΙΧΘΥΣ</th>
 * <td>ιχθυσ</td>
 * <td>lowercased all chars in String</td>
 * </tr>
 * </tbody>
 * </table>
 *
 * @param locale use the case transformation rules for this locale
 * @return the {@code String}, converted to lowercase.
 * @see java.lang.String#toLowerCase()
 * @see java.lang.String#toUpperCase()
 * @see java.lang.String#toUpperCase(Locale)
 * @since 1.1
 */
 public String toLowerCase(Locale locale) {
 return isLatin1() ? StringLatin1.toLowerCase(this, value, locale)
 : StringUTF16.toLowerCase(this, value, locale);
 }

 /**
 * Converts all of the characters in this {@code String} to lower
 * case using the rules of the default locale. This method is equivalent to
 * {@code toLowerCase(Locale.getDefault())}.
 * 
 * Note: This method is locale sensitive, and may produce unexpected
 * results if used for strings that are intended to be interpreted locale
 * independently.
 * Examples are programming language identifiers, protocol keys, and HTML
 * tags.
 * For instance, {@code "TITLE".toLowerCase()} in a Turkish locale
 * returns {@code "t\u005Cu0131tle"}, where '\u005Cu0131' is the
 * LATIN SMALL LETTER DOTLESS I character.
 * To obtain correct results for locale insensitive strings, use
 * {@code toLowerCase(Locale.ROOT)}.
 *
 * @return the {@code String}, converted to lowercase.
 * @see java.lang.String#toLowerCase(Locale)
 */
 public String toLowerCase() {
 return toLowerCase(Locale.getDefault());
 }

 /**
 * Converts all of the characters in this {@code String} to upper
 * case using the rules of the given {@code Locale}. Case mapping is based
 * on the Unicode Standard version specified by the {@link java.lang.Character Character}
 * class. Since case mappings are not always 1:1 char mappings, the resulting {@code String}
 * and this {@code String} may differ in length.
 * 
 * Examples of locale-sensitive and 1:M case mappings are in the following table:
 * <table class="plain">
 * <caption style="display:none">Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.</caption>
 * <thead>
 * <tr>
 * <th scope="col">Language Code of Locale</th>
 * <th scope="col">Lower Case</th>
 * <th scope="col">Upper Case</th>
 * <th scope="col">Description</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr>
 * <td>tr (Turkish)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">\u0069</th>
 * <td>\u0130</td>
 * <td>small letter i -> capital letter I with dot above</td>
 * </tr>
 * <tr>
 * <td>tr (Turkish)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">\u0131</th>
 * <td>\u0049</td>
 * <td>small letter dotless i -> capital letter I</td>
 * </tr>
 * <tr>
 * <td>(all)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">\u00df</th>
 * <td>\u0053 \u0053</td>
 * <td>small letter sharp s -> two letters: SS</td>
 * </tr>
 * <tr>
 * <td>(all)</td>
 * <th scope="row" style="font-weight:normal; text-align:left">Fahrvergnügen</th>
 * <td>FAHRVERGNÜGEN</td>
 * <td></td>
 * </tr>
 * </tbody>
 * </table>
 * @param locale use the case transformation rules for this locale
 * @return the {@code String}, converted to uppercase.
 * @see java.lang.String#toUpperCase()
 * @see java.lang.String#toLowerCase()
 * @see java.lang.String#toLowerCase(Locale)
 * @since 1.1
 */
 public String toUpperCase(Locale locale) {
 return isLatin1() ? StringLatin1.toUpperCase(this, value, locale)
 : StringUTF16.toUpperCase(this, value, locale);
 }

 /**
 * Converts all of the characters in this {@code String} to upper
 * case using the rules of the default locale. This method is equivalent to
 * {@code toUpperCase(Locale.getDefault())}.
 * 
 * Note: This method is locale sensitive, and may produce unexpected
 * results if used for strings that are intended to be interpreted locale
 * independently.
 * Examples are programming language identifiers, protocol keys, and HTML
 * tags.
 * For instance, {@code "title".toUpperCase()} in a Turkish locale
 * returns {@code "T\u005Cu0130TLE"}, where '\u005Cu0130' is the
 * LATIN CAPITAL LETTER I WITH DOT ABOVE character.
 * To obtain correct results for locale insensitive strings, use
 * {@code toUpperCase(Locale.ROOT)}.
 *
 * @return the {@code String}, converted to uppercase.
 * @see java.lang.String#toUpperCase(Locale)
 */
 public String toUpperCase() {
 return toUpperCase(Locale.getDefault());
 }

 /**
 * Returns a string whose value is this string, with all leading
 * and trailing space removed, where space is defined
 * as any character whose codepoint is less than or equal to
 * {@code 'U+0020'} (the space character).
 * 
 * If this {@code String} object represents an empty character
 * sequence, or the first and last characters of character sequence
 * represented by this {@code String} object both have codes
 * that are not space (as defined above), then a
 * reference to this {@code String} object is returned.
 * 
 * Otherwise, if all characters in this string are space (as
 * defined above), then a {@code String} object representing an
 * empty string is returned.
 * 
 * Otherwise, let k be the index of the first character in the
 * string whose code is not a space (as defined above) and let
 * m be the index of the last character in the string whose code
 * is not a space (as defined above). A {@code String}
 * object is returned, representing the substring of this string that
 * begins with the character at index k and ends with the
 * character at index m-that is, the result of
 * {@code this.substring(k, m + 1)}.
 * 
 * This method may be used to trim space (as defined above) from
 * the beginning and end of a string.
 *
 * @return a string whose value is this string, with all leading
 * and trailing space removed, or this string if it
 * has no leading or trailing space.
 */
 public String trim() {
 String ret = isLatin1() ? StringLatin1.trim(value)
 : StringUTF16.trim(value);
 return ret == null ? this : ret;
 }

 /**
 * Returns a string whose value is this string, with all leading
 * and trailing {@linkplain Character#isWhitespace(int) white space}
 * removed.
 * 
 * If this {@code String} object represents an empty string,
 * or if all code points in this string are
 * {@linkplain Character#isWhitespace(int) white space}, then an empty string
 * is returned.
 * 
 * Otherwise, returns a substring of this string beginning with the first
 * code point that is not a {@linkplain Character#isWhitespace(int) white space}
 * up to and including the last code point that is not a
 * {@linkplain Character#isWhitespace(int) white space}.
 * 
 * This method may be used to strip
 * {@linkplain Character#isWhitespace(int) white space} from
 * the beginning and end of a string.
 *
 * @return a string whose value is this string, with all leading
 * and trailing white space removed
 *
 * @see Character#isWhitespace(int)
 *
 * @since 11
 */
 public String strip() {
 String ret = isLatin1() ? StringLatin1.strip(value)
 : StringUTF16.strip(value);
 return ret == null ? this : ret;
 }

 /**
 * Returns a string whose value is this string, with all leading
 * {@linkplain Character#isWhitespace(int) white space} removed.
 * 
 * If this {@code String} object represents an empty string,
 * or if all code points in this string are
 * {@linkplain Character#isWhitespace(int) white space}, then an empty string
 * is returned.
 * 
 * Otherwise, returns a substring of this string beginning with the first
 * code point that is not a {@linkplain Character#isWhitespace(int) white space}
 * up to and including the last code point of this string.
 * 
 * This method may be used to trim
 * {@linkplain Character#isWhitespace(int) white space} from
 * the beginning of a string.
 *
 * @return a string whose value is this string, with all leading white
 * space removed
 *
 * @see Character#isWhitespace(int)
 *
 * @since 11
 */
 public String stripLeading() {
 String ret = isLatin1() ? StringLatin1.stripLeading(value)
 : StringUTF16.stripLeading(value);
 return ret == null ? this : ret;
 }

 /**
 * Returns a string whose value is this string, with all trailing
 * {@linkplain Character#isWhitespace(int) white space} removed.
 * 
 * If this {@code String} object represents an empty string,
 * or if all characters in this string are
 * {@linkplain Character#isWhitespace(int) white space}, then an empty string
 * is returned.
 * 
 * Otherwise, returns a substring of this string beginning with the first
 * code point of this string up to and including the last code point
 * that is not a {@linkplain Character#isWhitespace(int) white space}.
 * 
 * This method may be used to trim
 * {@linkplain Character#isWhitespace(int) white space} from
 * the end of a string.
 *
 * @return a string whose value is this string, with all trailing white
 * space removed
 *
 * @see Character#isWhitespace(int)
 *
 * @since 11
 */
 public String stripTrailing() {
 String ret = isLatin1() ? StringLatin1.stripTrailing(value)
 : StringUTF16.stripTrailing(value);
 return ret == null ? this : ret;
 }

 /**
 * Returns {@code true} if the string is empty or contains only
 * {@linkplain Character#isWhitespace(int) white space} codepoints,
 * otherwise {@code false}.
 *
 * @return {@code true} if the string is empty or contains only
 * {@linkplain Character#isWhitespace(int) white space} codepoints,
 * otherwise {@code false}
 *
 * @see Character#isWhitespace(int)
 *
 * @since 11
 */
 public boolean isBlank() {
 return indexOfNonWhitespace() == length();
 }

 /**
 * Returns a stream of lines extracted from this string,
 * separated by line terminators.
 * 
 * A line terminator is one of the following:
 * a line feed character {@code "\n"} (U+000A),
 * a carriage return character {@code "\r"} (U+000D),
 * or a carriage return followed immediately by a line feed
 * {@code "\r\n"} (U+000D U+000A).
 * 
 * A line is either a sequence of zero or more characters
 * followed by a line terminator, or it is a sequence of one or
 * more characters followed by the end of the string. A
 * line does not include the line terminator.
 * 
 * The stream returned by this method contains the lines from
 * this string in the order in which they occur.
 *
 * @apiNote This definition of line implies that an empty
 * string has zero lines and that there is no empty line
 * following a line terminator at the end of a string.
 *
 * @implNote This method provides better performance than
 * split("\R") by supplying elements lazily and
 * by faster search of new line terminators.
 *
 * @return the stream of lines extracted from this string
 *
 * @since 11
 */
 public Stream<String> lines() {
 return isLatin1() ? StringLatin1.lines(value) : StringUTF16.lines(value);
 }

 /**
 * Adjusts the indentation of each line of this string based on the value of
 * {@code n}, and normalizes line termination characters.
 * 
 * This string is conceptually separated into lines using
 * {@link String#lines()}. Each line is then adjusted as described below
 * and then suffixed with a line feed {@code "\n"} (U+000A). The resulting
 * lines are then concatenated and returned.
 * 
 * If {@code n > 0} then {@code n} spaces (U+0020) are inserted at the
 * beginning of each line.
 * 
 * If {@code n < 0} then up to {@code n}
 * {@linkplain Character#isWhitespace(int) white space characters} are removed
 * from the beginning of each line. If a given line does not contain
 * sufficient white space then all leading
 * {@linkplain Character#isWhitespace(int) white space characters} are removed.
 * Each white space character is treated as a single character. In
 * particular, the tab character {@code "\t"} (U+0009) is considered a
 * single character; it is not expanded.
 * 
 * If {@code n == 0} then the line remains unchanged. However, line
 * terminators are still normalized.
 *
 * @param n number of leading
 * {@linkplain Character#isWhitespace(int) white space characters}
 * to add or remove
 *
 * @return string with indentation adjusted and line endings normalized
 *
 * @see String#lines()
 * @see String#isBlank()
 * @see Character#isWhitespace(int)
 *
 * @since 12
 */
 public String indent(int n) {
 if (isEmpty()) {
 return "";
 }
 Stream<String> stream = lines();
 if (n > 0) {
 final String spaces = " ".repeat(n);
 stream = stream.map(s -> spaces + s);
 } else if (n == Integer.MIN_VALUE) {
 stream = stream.map(s -> s.stripLeading());
 } else if (n < 0) {
 stream = stream.map(s -> s.substring(Math.min(-n, s.indexOfNonWhitespace())));
 }
 return stream.collect(Collectors.joining("\n", "", "\n"));
 }

 private int indexOfNonWhitespace() {
 return isLatin1() ? StringLatin1.indexOfNonWhitespace(value)
 : StringUTF16.indexOfNonWhitespace(value);
 }

 private int lastIndexOfNonWhitespace() {
 return isLatin1() ? StringLatin1.lastIndexOfNonWhitespace(value)
 : StringUTF16.lastIndexOfNonWhitespace(value);
 }

 /**
 * Returns a string whose value is this string, with incidental
 * {@linkplain Character#isWhitespace(int) white space} removed from
 * the beginning and end of every line.
 * 
 * Incidental {@linkplain Character#isWhitespace(int) white space}
 * is often present in a text block to align the content with the opening
 * delimiter. For example, in the following code, dots represent incidental
 * {@linkplain Character#isWhitespace(int) white space}:
 * <blockquote><pre>
 * String html = """
 * ..............<html>
 * .............. <body>
 * .............. Hello, world
 * .............. </body>
 * ..............</html>
 * ..............""";
 * </pre></blockquote>
 * This method treats the incidental
 * {@linkplain Character#isWhitespace(int) white space} as indentation to be
 * stripped, producing a string that preserves the relative indentation of
 * the content. Using | to visualize the start of each line of the string:
 * <blockquote><pre>
 * |<html>
 * | <body>
 * | Hello, world
 * | </body>
 * |</html>
 * </pre></blockquote>
 * First, the individual lines of this string are extracted. A line
 * is a sequence of zero or more characters followed by either a line
 * terminator or the end of the string.
 * If the string has at least one line terminator, the last line consists
 * of the characters between the last terminator and the end of the string.
 * Otherwise, if the string has no terminators, the last line is the start
 * of the string to the end of the string, in other words, the entire
 * string.
 * A line does not include the line terminator.
 * 
 * Then, the minimum indentation (min) is determined as follows:
 * <ul>
 * <li>For each non-blank line (as defined by {@link String#isBlank()}),
 * the leading {@linkplain Character#isWhitespace(int) white space}
 * characters are counted.
 * </li>
 * <li>The leading {@linkplain Character#isWhitespace(int) white space}
 * characters on the last line are also counted even if
 * {@linkplain String#isBlank() blank}.
 * </li>
 * </ul>
 * The min value is the smallest of these counts.
 * 
 * For each {@linkplain String#isBlank() non-blank} line, min leading
 * {@linkplain Character#isWhitespace(int) white space} characters are
 * removed, and any trailing {@linkplain Character#isWhitespace(int) white
 * space} characters are removed. {@linkplain String#isBlank() Blank} lines
 * are replaced with the empty string.
 *
 * 
 * Finally, the lines are joined into a new string, using the LF character
 * {@code "\n"} (U+000A) to separate lines.
 *
 * @apiNote
 * This method's primary purpose is to shift a block of lines as far as
 * possible to the left, while preserving relative indentation. Lines
 * that were indented the least will thus have no leading
 * {@linkplain Character#isWhitespace(int) white space}.
 * The result will have the same number of line terminators as this string.
 * If this string ends with a line terminator then the result will end
 * with a line terminator.
 *
 * @implSpec
 * This method treats all {@linkplain Character#isWhitespace(int) white space}
 * characters as having equal width. As long as the indentation on every
 * line is consistently composed of the same character sequences, then the
 * result will be as described above.
 *
 * @return string with incidental indentation removed and line
 * terminators normalized
 *
 * @see String#lines()
 * @see String#isBlank()
 * @see String#indent(int)
 * @see Character#isWhitespace(int)
 *
 * @since 15
 *
 */
 public String stripIndent() {
 int length = length();
 if (length == 0) {
 return "";
 }
 char lastChar = charAt(length - 1);
 boolean optOut = lastChar == '\n' || lastChar == '\r';
 List<String> lines = lines().toList();
 final int outdent = optOut ? 0 : outdent(lines);
 return lines.stream()
 .map(line -> {
 int firstNonWhitespace = line.indexOfNonWhitespace();
 int lastNonWhitespace = line.lastIndexOfNonWhitespace();
 int incidentalWhitespace = Math.min(outdent, firstNonWhitespace);
 return firstNonWhitespace > lastNonWhitespace
 ? "" : line.substring(incidentalWhitespace, lastNonWhitespace);
 })
 .collect(Collectors.joining("\n", "", optOut ? "\n" : ""));
 }

 private static int outdent(List<String> lines) {
 // Note: outdent is guaranteed to be zero or positive number.
 // If there isn't a non-blank line then the last must be blank
 int outdent = Integer.MAX_VALUE;
 for (String line : lines) {
 int leadingWhitespace = line.indexOfNonWhitespace();
 if (leadingWhitespace != line.length()) {
 outdent = Integer.min(outdent, leadingWhitespace);
 }
 }
 String lastLine = lines.get(lines.size() - 1);
 if (lastLine.isBlank()) {
 outdent = Integer.min(outdent, lastLine.length());
 }
 return outdent;
 }

 /**
 * Returns a string whose value is this string, with escape sequences
 * translated as if in a string literal.
 * 
 * Escape sequences are translated as follows;
 * <table class="striped">
 * <caption style="display:none">Translation</caption>
 * <thead>
 * <tr>
 * <th scope="col">Escape</th>
 * <th scope="col">Name</th>
 * <th scope="col">Translation</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr>
 * <th scope="row">{@code \u005Cb}</th>
 * <td>backspace</td>
 * <td>{@code U+0008}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005Ct}</th>
 * <td>horizontal tab</td>
 * <td>{@code U+0009}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005Cn}</th>
 * <td>line feed</td>
 * <td>{@code U+000A}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005Cf}</th>
 * <td>form feed</td>
 * <td>{@code U+000C}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005Cr}</th>
 * <td>carriage return</td>
 * <td>{@code U+000D}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005Cs}</th>
 * <td>space</td>
 * <td>{@code U+0020}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005C"}</th>
 * <td>double quote</td>
 * <td>{@code U+0022}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005C'}</th>
 * <td>single quote</td>
 * <td>{@code U+0027}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005C\u005C}</th>
 * <td>backslash</td>
 * <td>{@code U+005C}</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005C0 - \u005C377}</th>
 * <td>octal escape</td>
 * <td>code point equivalents</td>
 * </tr>
 * <tr>
 * <th scope="row">{@code \u005C<line-terminator>}</th>
 * <td>continuation</td>
 * <td>discard</td>
 * </tr>
 * </tbody>
 * </table>
 *
 * @implNote
 * This method does not translate Unicode escapes such as "{@code \u005cu2022}".
 * Unicode escapes are translated by the Java compiler when reading input characters and
 * are not part of the string literal specification.
 *
 * @throws IllegalArgumentException when an escape sequence is malformed.
 *
 * @return String with escape sequences translated.
 *
 * @jls 3.10.7 Escape Sequences
 *
 * @since 15
 */
 public String translateEscapes() {
 if (isEmpty()) {
 return "";
 }
 char[] chars = toCharArray();
 int length = chars.length;
 int from = 0;
 int to = 0;
 while (from < length) {
 char ch = chars[from++];
 if (ch == '\\') {
 ch = from < length ? chars[from++] : '\0';
 switch (ch) {
 case 'b':
 ch = '\b';
 break;
 case 'f':
 ch = '\f';
 break;
 case 'n':
 ch = '\n';
 break;
 case 'r':
 ch = '\r';
 break;
 case 's':
 ch = ' ';
 break;
 case 't':
 ch = '\t';
 break;
 case '\'':
 case '\"':
 case '\\':
 // as is
 break;
 case '0': case '1': case '2': case '3':
 case '4': case '5': case '6': case '7':
 int limit = Integer.min(from + (ch <= '3' ? 2 : 1), length);
 int code = ch - '0';
 while (from < limit) {
 ch = chars[from];
 if (ch < '0' || '7' < ch) {
 break;
 }
 from++;
 code = (code << 3) | (ch - '0');
 }
 ch = (char)code;
 break;
 case '\n':
 continue;
 case '\r':
 if (from < length && chars[from] == '\n') {
 from++;
 }
 continue;
 default: {
 String msg = String.format(
 "Invalid escape sequence: \\%c \\\\u%04X",
 ch, (int)ch);
 throw new IllegalArgumentException(msg);
 }
 }
 }

 chars[to++] = ch;
 }

 return new String(chars, 0, to);
 }

 /**
 * This method allows the application of a function to {@code this}
 * string. The function should expect a single String argument
 * and produce an {@code R} result.
 * 
 * Any exception thrown by {@code f.apply()} will be propagated to the
 * caller.
 *
 * @param f a function to apply
 *
 * @param <R> the type of the result
 *
 * @return the result of applying the function to this string
 *
 * @see java.util.function.Function
 *
 * @since 12
 */
 public <R> R transform(Function<? super String, ? extends R> f) {
 return f.apply(this);
 }

 /**
 * This object (which is already a string!) is itself returned.
 *
 * @return the string itself.
 */
 public String toString() {
 return this;
 }

 /**
 * Returns a stream of {@code int} zero-extending the {@code char} values
 * from this sequence. Any char which maps to a <a
 * href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate code
 * point</a> is passed through uninterpreted.
 *
 * @return an IntStream of char values from this sequence
 * @since 9
 */
 @Override
 public IntStream chars() {
 return StreamSupport.intStream(
 isLatin1() ? new StringLatin1.CharsSpliterator(value, Spliterator.IMMUTABLE)
 : new StringUTF16.CharsSpliterator(value, Spliterator.IMMUTABLE),
 false);
 }

 /**
 * Returns a stream of code point values from this sequence. Any surrogate
 * pairs encountered in the sequence are combined as if by {@linkplain
 * Character#toCodePoint Character.toCodePoint} and the result is passed
 * to the stream. Any other code units, including ordinary BMP characters,
 * unpaired surrogates, and undefined code units, are zero-extended to
 * {@code int} values which are then passed to the stream.
 *
 * @return an IntStream of Unicode code points from this sequence
 * @since 9
 */
 @Override
 public IntStream codePoints() {
 return StreamSupport.intStream(
 isLatin1() ? new StringLatin1.CharsSpliterator(value, Spliterator.IMMUTABLE)
 : new StringUTF16.CodePointsSpliterator(value, Spliterator.IMMUTABLE),
 false);
 }

 /**
 * Converts this string to a new character array.
 *
 * @return a newly allocated character array whose length is the length
 * of this string and whose contents are initialized to contain
 * the character sequence represented by this string.
 */
 public char[] toCharArray() {
 return isLatin1() ? StringLatin1.toChars(value)
 : StringUTF16.toChars(value);
 }

 /**
 * Returns a formatted string using the specified format string and
 * arguments.
 *
 * The locale always used is the one returned by {@link
 * java.util.Locale#getDefault(java.util.Locale.Category)
 * Locale.getDefault(Locale.Category)} with
 * {@link java.util.Locale.Category#FORMAT FORMAT} category specified.
 *
 * @param format
 * A <a href="../util/Formatter.html#syntax">format string</a>
 *
 * @param args
 * Arguments referenced by the format specifiers in the format
 * string. If there are more arguments than format specifiers, the
 * extra arguments are ignored. The number of arguments is
 * variable and may be zero. The maximum number of arguments is
 * limited by the maximum dimension of a Java array as defined by
 * <cite>The Java Virtual Machine Specification</cite>.
 * The behaviour on a
 * {@code null} argument depends on the <a
 * href="../util/Formatter.html#syntax">conversion</a>.
 *
 * @throws java.util.IllegalFormatException
 * If a format string contains an illegal syntax, a format
 * specifier that is incompatible with the given arguments,
 * insufficient arguments given the format string, or other
 * illegal conditions. For specification of all possible
 * formatting errors, see the <a
 * href="../util/Formatter.html#detail">Details</a> section of the
 * formatter class specification.
 *
 * @return A formatted string
 *
 * @see java.util.Formatter
 * @since 1.5
 */
 public static String format(String format, Object... args) {
 return new Formatter().format(format, args).toString();
 }

 /**
 * Returns a formatted string using the specified locale, format string,
 * and arguments.
 *
 * @param l
 * The {@linkplain java.util.Locale locale} to apply during
 * formatting. If {@code l} is {@code null} then no localization
 * is applied.
 *
 * @param format
 * A <a href="../util/Formatter.html#syntax">format string</a>
 *
 * @param args
 * Arguments referenced by the format specifiers in the format
 * string. If there are more arguments than format specifiers, the
 * extra arguments are ignored. The number of arguments is
 * variable and may be zero. The maximum number of arguments is
 * limited by the maximum dimension of a Java array as defined by
 * <cite>The Java Virtual Machine Specification</cite>.
 * The behaviour on a
 * {@code null} argument depends on the
 * <a href="../util/Formatter.html#syntax">conversion</a>.
 *
 * @throws java.util.IllegalFormatException
 * If a format string contains an illegal syntax, a format
 * specifier that is incompatible with the given arguments,
 * insufficient arguments given the format string, or other
 * illegal conditions. For specification of all possible
 * formatting errors, see the <a
 * href="../util/Formatter.html#detail">Details</a> section of the
 * formatter class specification
 *
 * @return A formatted string
 *
 * @see java.util.Formatter
 * @since 1.5
 */
 public static String format(Locale l, String format, Object... args) {
 return new Formatter(l).format(format, args).toString();
 }

 /**
 * Formats using this string as the format string, and the supplied
 * arguments.
 *
 * @implSpec This method is equivalent to {@code String.format(this, args)}.
 *
 * @param args
 * Arguments referenced by the format specifiers in this string.
 *
 * @return A formatted string
 *
 * @see java.lang.String#format(String,Object...)
 * @see java.util.Formatter
 *
 * @since 15
 *
 */
 public String formatted(Object... args) {
 return new Formatter().format(this, args).toString();
 }

 /**
 * Returns the string representation of the {@code Object} argument.
 *
 * @param obj an {@code Object}.
 * @return if the argument is {@code null}, then a string equal to
 * {@code "null"}; otherwise, the value of
 * {@code obj.toString()} is returned.
 * @see java.lang.Object#toString()
 */
 public static String valueOf(Object obj) {
 return (obj == null) ? "null" : obj.toString();
 }

 /**
 * Returns the string representation of the {@code char} array
 * argument. The contents of the character array are copied; subsequent
 * modification of the character array does not affect the returned
 * string.
 *
 * @param data the character array.
 * @return a {@code String} that contains the characters of the
 * character array.
 */
 public static String valueOf(char[] data) {
 return new String(data);
 }

 /**
 * Returns the string representation of a specific subarray of the
 * {@code char} array argument.
 * 
 * The {@code offset} argument is the index of the first
 * character of the subarray. The {@code count} argument
 * specifies the length of the subarray. The contents of the subarray
 * are copied; subsequent modification of the character array does not
 * affect the returned string.
 *
 * @param data the character array.
 * @param offset initial offset of the subarray.
 * @param count length of the subarray.
 * @return a {@code String} that contains the characters of the
 * specified subarray of the character array.
 * @throws IndexOutOfBoundsException if {@code offset} is
 * negative, or {@code count} is negative, or
 * {@code offset+count} is larger than
 * {@code data.length}.
 */
 public static String valueOf(char[] data, int offset, int count) {
 return new String(data, offset, count);
 }

 /**
 * Equivalent to {@link #valueOf(char[], int, int)}.
 *
 * @param data the character array.
 * @param offset initial offset of the subarray.
 * @param count length of the subarray.
 * @return a {@code String} that contains the characters of the
 * specified subarray of the character array.
 * @throws IndexOutOfBoundsException if {@code offset} is
 * negative, or {@code count} is negative, or
 * {@code offset+count} is larger than
 * {@code data.length}.
 */
 public static String copyValueOf(char[] data, int offset, int count) {
 return new String(data, offset, count);
 }

 /**
 * Equivalent to {@link #valueOf(char[])}.
 *
 * @param data the character array.
 * @return a {@code String} that contains the characters of the
 * character array.
 */
 public static String copyValueOf(char[] data) {
 return new String(data);
 }

 /**
 * Returns the string representation of the {@code boolean} argument.
 *
 * @param b a {@code boolean}.
 * @return if the argument is {@code true}, a string equal to
 * {@code "true"} is returned; otherwise, a string equal to
 * {@code "false"} is returned.
 */
 public static String valueOf(boolean b) {
 return b ? "true" : "false";
 }

 /**
 * Returns the string representation of the {@code char}
 * argument.
 *
 * @param c a {@code char}.
 * @return a string of length {@code 1} containing
 * as its single character the argument {@code c}.
 */
 public static String valueOf(char c) {
 if (COMPACT_STRINGS && StringLatin1.canEncode(c)) {
 return new String(StringLatin1.toBytes(c), LATIN1);
 }
 return new String(StringUTF16.toBytes(c), UTF16);
 }

 /**
 * Returns the string representation of the {@code int} argument.
 * 
 * The representation is exactly the one returned by the
 * {@code Integer.toString} method of one argument.
 *
 * @param i an {@code int}.
 * @return a string representation of the {@code int} argument.
 * @see java.lang.Integer#toString(int, int)
 */
 public static String valueOf(int i) {
 return Integer.toString(i);
 }

 /**
 * Returns the string representation of the {@code long} argument.
 * 
 * The representation is exactly the one returned by the
 * {@code Long.toString} method of one argument.
 *
 * @param l a {@code long}.
 * @return a string representation of the {@code long} argument.
 * @see java.lang.Long#toString(long)
 */
 public static String valueOf(long l) {
 return Long.toString(l);
 }

 /**
 * Returns the string representation of the {@code float} argument.
 * 
 * The representation is exactly the one returned by the
 * {@code Float.toString} method of one argument.
 *
 * @param f a {@code float}.
 * @return a string representation of the {@code float} argument.
 * @see java.lang.Float#toString(float)
 */
 public static String valueOf(float f) {
 return Float.toString(f);
 }

 /**
 * Returns the string representation of the {@code double} argument.
 * 
 * The representation is exactly the one returned by the
 * {@code Double.toString} method of one argument.
 *
 * @param d a {@code double}.
 * @return a string representation of the {@code double} argument.
 * @see java.lang.Double#toString(double)
 */
 public static String valueOf(double d) {
 return Double.toString(d);
 }

 /**
 * Returns a canonical representation for the string object.
 * 
 * A pool of strings, initially empty, is maintained privately by the
 * class {@code String}.
 * 
 * When the intern method is invoked, if the pool already contains a
 * string equal to this {@code String} object as determined by
 * the {@link #equals(Object)} method, then the string from the pool is
 * returned. Otherwise, this {@code String} object is added to the
 * pool and a reference to this {@code String} object is returned.
 * 
 * It follows that for any two strings {@code s} and {@code t},
 * {@code s.intern() == t.intern()} is {@code true}
 * if and only if {@code s.equals(t)} is {@code true}.
 * 
 * All literal strings and string-valued constant expressions are
 * interned. String literals are defined in section {@jls 3.10.5} of the
 * <cite>The Java Language Specification</cite>.
 *
 * @return a string that has the same contents as this string, but is
 * guaranteed to be from a pool of unique strings.
 */
 public native String intern();

 /**
 * Returns a string whose value is the concatenation of this
 * string repeated {@code count} times.
 * 
 * If this string is empty or count is zero then the empty
 * string is returned.
 *
 * @param count number of times to repeat
 *
 * @return A string composed of this string repeated
 * {@code count} times or the empty string if this
 * string is empty or count is zero
 *
 * @throws IllegalArgumentException if the {@code count} is
 * negative.
 *
 * @since 11
 */
 public String repeat(int count) {
 if (count < 0) {
 throw new IllegalArgumentException("count is negative: " + count);
 }
 if (count == 1) {
 return this;
 }
 final int len = value.length;
 if (len == 0 || count == 0) {
 return "";
 }
 if (Integer.MAX_VALUE / count < len) {
 throw new OutOfMemoryError("Required length exceeds implementation limit");
 }
 if (len == 1) {
 final byte[] single = new byte[count];
 Arrays.fill(single, value[0]);
 return new String(single, coder);
 }
 final int limit = len * count;
 final byte[] multiple = new byte[limit];
 System.arraycopy(value, 0, multiple, 0, len);
 int copied = len;
 for (; copied < limit - copied; copied <<= 1) {
 System.arraycopy(multiple, 0, multiple, copied, copied);
 }
 System.arraycopy(multiple, 0, multiple, copied, limit - copied);
 return new String(multiple, coder);
 }

 ////////////////////////////////////////////////////////////////

 /**
 * Copy character bytes from this string into dst starting at dstBegin.
 * This method doesn't perform any range checking.
 *
 * Invoker guarantees: dst is in UTF16 (inflate itself for asb), if two
 * coders are different, and dst is big enough (range check)
 *
 * @param dstBegin the char index, not offset of byte[]
 * @param coder the coder of dst[]
 */
 void getBytes(byte[] dst, int dstBegin, byte coder) {
 if (coder() == coder) {
 System.arraycopy(value, 0, dst, dstBegin << coder, value.length);
 } else { // this.coder == LATIN && coder == UTF16
 StringLatin1.inflate(value, 0, dst, dstBegin, value.length);
 }
 }

 /**
 * Copy character bytes from this string into dst starting at dstBegin.
 * This method doesn't perform any range checking.
 *
 * Invoker guarantees: dst is in UTF16 (inflate itself for asb), if two
 * coders are different, and dst is big enough (range check)
 *
 * @param srcPos the char index, not offset of byte[]
 * @param dstBegin the char index to start from
 * @param coder the coder of dst[]
 * @param length the amount of copied chars
 */
 void getBytes(byte[] dst, int srcPos, int dstBegin, byte coder, int length) {
 if (coder() == coder) {
 System.arraycopy(value, srcPos << coder, dst, dstBegin << coder, length << coder);
 } else { // this.coder == LATIN && coder == UTF16
 StringLatin1.inflate(value, srcPos, dst, dstBegin, length);
 }
 }

 /*
 * Package private constructor. Trailing Void argument is there for
 * disambiguating it against other (public) constructors.
 *
 * Stores the char[] value into a byte[] that each byte represents
 * the8 low-order bits of the corresponding character, if the char[]
 * contains only latin1 character. Or a byte[] that stores all
 * characters in their byte sequences defined by the {@code StringUTF16}.
 */
 String(char[] value, int off, int len, Void sig) {
 if (len == 0) {
 this.value = "".value;
 this.coder = "".coder;
 return;
 }
 if (COMPACT_STRINGS) {
 byte[] val = StringUTF16.compress(value, off, len);
 if (val != null) {
 this.value = val;
 this.coder = LATIN1;
 return;
 }
 }
 this.coder = UTF16;
 this.value = StringUTF16.toBytes(value, off, len);
 }

 /*
 * Package private constructor. Trailing Void argument is there for
 * disambiguating it against other (public) constructors.
 */
 String(AbstractStringBuilder asb, Void sig) {
 byte[] val = asb.getValue();
 int length = asb.length();
 if (asb.isLatin1()) {
 this.coder = LATIN1;
 this.value = Arrays.copyOfRange(val, 0, length);
 } else {
 // only try to compress val if some characters were deleted.
 if (COMPACT_STRINGS && asb.maybeLatin1) {
 byte[] buf = StringUTF16.compress(val, 0, length);
 if (buf != null) {
 this.coder = LATIN1;
 this.value = buf;
 return;
 }
 }
 this.coder = UTF16;
 this.value = Arrays.copyOfRange(val, 0, length << 1);
 }
 }

 /*
 * Package private constructor which shares value array for speed.
 */
 String(byte[] value, byte coder) {
 this.value = value;
 this.coder = coder;
 }

 byte coder() {
 return COMPACT_STRINGS ? coder : UTF16;
 }

 byte[] value() {
 return value;
 }

 boolean isLatin1() {
 return COMPACT_STRINGS && coder == LATIN1;
 }

 @Native static final byte LATIN1 = 0;
 @Native static final byte UTF16 = 1;

 /*
 * StringIndexOutOfBoundsException if {@code index} is
 * negative or greater than or equal to {@code length}.
 */
 static void checkIndex(int index, int length) {
 Preconditions.checkIndex(index, length, Preconditions.SIOOBE_FORMATTER);
 }

 /*
 * StringIndexOutOfBoundsException if {@code offset}
 * is negative or greater than {@code length}.
 */
 static void checkOffset(int offset, int length) {
 Preconditions.checkFromToIndex(offset, length, length, Preconditions.SIOOBE_FORMATTER);
 }

 /*
 * Check {@code offset}, {@code count} against {@code 0} and {@code length}
 * bounds.
 *
 * @return {@code offset} if the sub-range within bounds of the range
 * @throws StringIndexOutOfBoundsException
 * If {@code offset} is negative, {@code count} is negative,
 * or {@code offset} is greater than {@code length - count}
 */
 static int checkBoundsOffCount(int offset, int count, int length) {
 return Preconditions.checkFromIndexSize(offset, count, length, Preconditions.SIOOBE_FORMATTER);
 }

 /*
 * Check {@code begin}, {@code end} against {@code 0} and {@code length}
 * bounds.
 *
 * @throws StringIndexOutOfBoundsException
 * If {@code begin} is negative, {@code begin} is greater than
 * {@code end}, or {@code end} is greater than {@code length}.
 */
 static void checkBoundsBeginEnd(int begin, int end, int length) {
 Preconditions.checkFromToIndex(begin, end, length, Preconditions.SIOOBE_FORMATTER);
 }

 /**
 * Returns the string representation of the {@code codePoint}
 * argument.
 *
 * @param codePoint a {@code codePoint}.
 * @return a string of length {@code 1} or {@code 2} containing
 * as its single character the argument {@code codePoint}.
 * @throws IllegalArgumentException if the specified
 * {@code codePoint} is not a {@linkplain Character#isValidCodePoint
 * valid Unicode code point}.
 */
 static String valueOfCodePoint(int codePoint) {
 if (COMPACT_STRINGS && StringLatin1.canEncode(codePoint)) {
 return new String(StringLatin1.toBytes((char)codePoint), LATIN1);
 } else if (Character.isBmpCodePoint(codePoint)) {
 return new String(StringUTF16.toBytes((char)codePoint), UTF16);
 } else if (Character.isSupplementaryCodePoint(codePoint)) {
 return new String(StringUTF16.toBytesSupplementary(codePoint), UTF16);
 }

 throw new IllegalArgumentException(
 format("Not a valid Unicode code point: 0x%X", codePoint));
 }

 /**
 * Returns an {@link Optional} containing the nominal descriptor for this
 * instance, which is the instance itself.
 *
 * @return an {@link Optional} describing the {@linkplain String} instance
 * @since 12
 */
 @Override
 public Optional<String> describeConstable() {
 return Optional.of(this);
 }

 /**
 * Resolves this instance as a {@link ConstantDesc}, the result of which is
 * the instance itself.
 *
 * @param lookup ignored
 * @return the {@linkplain String} instance
 * @since 12
 */
 @Override
 public String resolveConstantDesc(MethodHandles.Lookup lookup) {
 return this;
 }

}

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Cephes Mathematical Library

Wiener Entwicklungsmethode

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