深入Java—String源代码

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/*
* @(#)String.java 1.204 06/06/09
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/

package java.lang;

import java.io.ObjectStreamClass;
import java.io.ObjectStreamField;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Formatter;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
* The <code>String</code> class represents character strings. All
* string literals in Java programs, such as <code>"abc"</code>, 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</code> 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. String concatenation is implemented
* through the <code>StringBuilder</code>(or <code>StringBuffer</code>)
* class and its <code>append</code> method.
* String conversions are implemented through the method
* <code>toString</code>, defined by <code>Object</code> and
* inherited by all classes in Java. For additional information on
* string concatenation and conversion, see Gosling, Joy, and Steele,
* The Java Language Specification.
*
* Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* A <code>String</code> 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</code> class for
* more information).
* Index values refer to <code>char</code> code units, so a supplementary
* character uses two positions in a <code>String</code>.
* The <code>String</code> 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</code> values).
*
* @author Lee Boynton
* @author Arthur van Hoff
* @version 1.204, 06/09/06
* @see java.lang.Object#toString()
* @see java.lang.StringBuffer
* @see java.lang.StringBuilder
* @see java.nio.charset.Charset
* @since JDK1.0
*/

public final class String
implements java.io.Serializable, Comparable<String>, CharSequence
{
/** The value is used for character storage. */
private final char value[];

/** The offset is the first index of the storage that is used. */
private final int offset;

/** The count is the number of characters in the String. */
private final int count;

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

/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = -6849794470754667710L;

/**
* Class String is special cased within the Serialization Stream Protocol.
*
* A String instance is written initially into an ObjectOutputStream in the
* following format:
* <pre>
* <code>TC_STRING</code> (utf String)
* </pre>
* The String is written by method <code>DataOutput.writeUTF</code>.
* A new handle is generated to refer to all future references to the
* string instance within the stream.
*/
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.offset = 0;
this.count = 0;
this.value = new char[0];
}

/**
* 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}
*/
public String(String original) {
int size = original.count;
char[] originalValue = original.value;
char[] v;
if (originalValue.length > size) {
// The array representing the String is bigger than the new
// String itself. Perhaps this constructor is being called
// in order to trim the baggage, so make a copy of the array.
int off = original.offset;
v = Arrays.copyOfRange(originalValue, off, off+size);
} else {
// The array representing the String is the same
// size as the String, so no point in making a copy.
v = originalValue;
}
this.offset = 0;
this.count = size;
this.value = v;
}

/**
* 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[]) {
int size = value.length;
this.offset = 0;
this.count = size;
this.value = Arrays.copyOf(value, size);
}

/**
* 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 the {@code offset} and {@code count} arguments index
* characters outside the bounds of the {@code value} array
*/
public String(char value[], int offset, int count) {
if (offset < 0) {
throw new StringIndexOutOfBoundsException(offset);
}
if (count < 0) {
throw new StringIndexOutOfBoundsException(count);
}
// Note: offset or count might be near -1>>>1.
if (offset > value.length - count) {
throw new StringIndexOutOfBoundsException(offset + count);
}
this.offset = 0;
this.count = count;
this.value = Arrays.copyOfRange(value, offset, offset+count);
}

/**
* Allocates a new {@code String} that contains characters from a subarray
* of the Unicode code point 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 the {@code offset} and {@code count} arguments index
* characters outside the bounds of the {@code codePoints} array
*
* @since 1.5
*/
public String(int[] codePoints, int offset, int count) {
if (offset < 0) {
throw new StringIndexOutOfBoundsException(offset);
}
if (count < 0) {
throw new StringIndexOutOfBoundsException(count);
}
// Note: offset or count might be near -1>>>1.
if (offset > codePoints.length - count) {
throw new StringIndexOutOfBoundsException(offset + count);
}

int expansion = 0;
int margin = 1;
char[] v = new char[count + margin];
int x = offset;
int j = 0;
for (int i = 0; i < count; i++) {
int c = codePoints[x++];
if (c < 0) {
throw new IllegalArgumentException();
}
if (margin <= 0 && (j+1) >= v.length) {
if (expansion == 0) {
expansion = (((-margin + 1) * count) << 10) / i;
expansion >>= 10;
if (expansion <= 0) {
expansion = 1;
}
} else {
expansion *= 2;
}
int newLen = Math.min(v.length+expansion, count*2);
margin = (newLen - v.length) - (count - i);
v = Arrays.copyOf(v, newLen);
}
if (c < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
v[j++] = (char) c;
} else if (c <= Character.MAX_CODE_POINT) {
Character.toSurrogates(c, v, j);
j += 2;
margin--;
} else {
throw new IllegalArgumentException();
}
}
this.offset = 0;
this.value = v;
this.count = j;
}

/**
* 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 method above.
*
* @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
* java.nio.charset.Charset}, charset name, or that use the platform‘s
* 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 the {@code offset} or {@code count} argument is invalid
*
* @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
public String(byte ascii[], int hibyte, int offset, int count) {
checkBounds(ascii, offset, count);
char value[] = new char[count];

if (hibyte == 0) {
for (int i = count ; i-- > 0 ;) {
value[i] = (char) (ascii[i + offset] & 0xff);
}
} else {
hibyte <<= 8;
for (int i = count ; i-- > 0 ;) {
value[i] = (char) (hibyte | (ascii[i + offset] & 0xff));
}
}
this.offset = 0;
this.count = count;
this.value = value;
}

/**
* Allocates a new {@code String} containing characters constructed from
* an array of 8-bit integer values. Each character cin 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
* java.nio.charset.Charset}, charset name, or that use the platform‘s
* 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
public String(byte ascii[], int hibyte) {
this(ascii, hibyte, 0, ascii.length);
}

/* Common private utility method used to bounds check the byte array
* and requested offset & length values used by the String(byte[],..)
* constructors.
*/
private static void checkBounds(byte[] bytes, int offset, int length) {
if (length < 0)
throw new StringIndexOutOfBoundsException(length);
if (offset < 0)
throw new StringIndexOutOfBoundsException(offset);
if (offset > bytes.length - length)
throw new StringIndexOutOfBoundsException(offset + 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 the {@code offset} and {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since JDK1.1
*/
public String(byte bytes[], int offset, int length, String charsetName)
throws UnsupportedEncodingException
{
if (charsetName == null)
throw new NullPointerException("charsetName");
checkBounds(bytes, offset, length);
char[] v = StringCoding.decode(charsetName, bytes, offset, length);
this.offset = 0;
this.count = v.length;
this.value = v;
}

/**
* 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 the {@code offset} and {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since 1.6
*/
public String(byte bytes[], int offset, int length, Charset charset) {
if (charset == null)
throw new NullPointerException("charset");
checkBounds(bytes, offset, length);
char[] v = StringCoding.decode(charset, bytes, offset, length);
this.offset = 0;
this.count = v.length;
this.value = v;
}

/**
* 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 JDK1.1
*/
public String(byte bytes[], String charsetName)
throws UnsupportedEncodingException
{
this(bytes, 0, bytes.length, charsetName);
}

/**
* 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(bytes, 0, bytes.length, charset);
}

/**
* Constructs a new {@code String} by decoding the specified subarray of
* bytes using the platform‘s 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 the {@code offset} and the {@code length} arguments index
* characters outside the bounds of the {@code bytes} array
*
* @since JDK1.1
*/
public String(byte bytes[], int offset, int length) {
checkBounds(bytes, offset, length);
char[] v = StringCoding.decode(bytes, offset, length);
this.offset = 0;
this.count = v.length;
this.value = v;
}

/**
* Constructs a new {@code String} by decoding the specified array of bytes
* using the platform‘s 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 JDK1.1
*/
public String(byte bytes[]) {
this(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) {
String result = buffer.toString();
this.value = result.value;
this.count = result.count;
this.offset = result.offset;
}

/**
* 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) {
String result = builder.toString();
this.value = result.value;
this.count = result.count;
this.offset = result.offset;
}

// Package private constructor which shares value array for speed.
String(int offset, int count, char value[]) {
this.value = value;
this.offset = offset;
this.count = count;
}

/**
* 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 count;
}

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

/**
* Returns the <code>char</code> value at the
* specified index. An index ranges from <code>0</code> to
* <code>length() - 1</code>. The first <code>char</code> value of the sequence
* is at index <code>0</code>, the next at index <code>1</code>,
* and so on, as for array indexing.
*
* If the <code>char</code> 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</code> value.
* @return the <code>char</code> value at the specified index of this string.
* The first <code>char</code> value is at index <code>0</code>.
* @exception IndexOutOfBoundsException if the <code>index</code>
* argument is negative or not less than the length of this
* string.
*/
public char charAt(int index) {
if ((index < 0) || (index >= count)) {
throw new StringIndexOutOfBoundsException(index);
}
return value[index + offset];
}

/**
* Returns the character (Unicode code point) at the specified
* index. The index refers to <code>char</code> values
* (Unicode code units) and ranges from <code>0</code> to
* {@link #length()}<code> - 1</code>.
*
* If the <code>char</code> value specified at the given index
* is in the high-surrogate range, the following index is less
* than the length of this <code>String</code>, and the
* <code>char</code> 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</code> value at the given index is returned.
*
* @param index the index to the <code>char</code> values
* @return the code point value of the character at the
* <code>index</code>
* @exception IndexOutOfBoundsException if the <code>index</code>
* argument is negative or not less than the length of this
* string.
* @since 1.5
*/
public int codePointAt(int index) {
if ((index < 0) || (index >= count)) {
throw new StringIndexOutOfBoundsException(index);
}
return Character.codePointAtImpl(value, offset + index, offset + count);
}

/**
* Returns the character (Unicode code point) before the specified
* index. The index refers to <code>char</code> values
* (Unicode code units) and ranges from <code>1</code> to {@link
* CharSequence#length() length}.
*
* If the <code>char</code> value at <code>(index - 1)</code>
* is in the low-surrogate range, <code>(index - 2)</code> is not
* negative, and the <code>char</code> value at <code>(index -
* 2)</code> is in the high-surrogate range, then the
* supplementary code point value of the surrogate pair is
* returned. If the <code>char</code> value at <code>index -
* 1</code> 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.
* @exception IndexOutOfBoundsException if the <code>index</code>
* 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;
if ((i < 0) || (i >= count)) {
throw new StringIndexOutOfBoundsException(index);
}
return Character.codePointBeforeImpl(value, offset + index, offset);
}

/**
* Returns the number of Unicode code points in the specified text
* range of this <code>String</code>. The text range begins at the
* specified <code>beginIndex</code> and extends to the
* <code>char</code> at index <code>endIndex - 1</code>. Thus the
* length (in <code>char</code>s) of the text range is
* <code>endIndex-beginIndex</code>. Unpaired surrogates within
* the text range count as one code point each.
*
* @param beginIndex the index to the first <code>char</code> of
* the text range.
* @param endIndex the index after the last <code>char</code> of
* the text range.
* @return the number of Unicode code points in the specified text
* range
* @exception IndexOutOfBoundsException if the
* <code>beginIndex</code> is negative, or <code>endIndex</code>
* is larger than the length of this <code>String</code>, or
* <code>beginIndex</code> is larger than <code>endIndex</code>.
* @since 1.5
*/
public int codePointCount(int beginIndex, int endIndex) {
if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
throw new IndexOutOfBoundsException();
}
return Character.codePointCountImpl(value, offset+beginIndex, endIndex-beginIndex);
}

/**
* Returns the index within this <code>String</code> that is
* offset from the given <code>index</code> by
* <code>codePointOffset</code> code points. Unpaired surrogates
* within the text range given by <code>index</code> and
* <code>codePointOffset</code> 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</code>
* @exception IndexOutOfBoundsException if <code>index</code>
* is negative or larger then the length of this
* <code>String</code>, or if <code>codePointOffset</code> is positive
* and the substring starting with <code>index</code> has fewer
* than <code>codePointOffset</code> code points,
* or if <code>codePointOffset</code> is negative and the substring
* before <code>index</code> has fewer than the absolute value
* of <code>codePointOffset</code> code points.
* @since 1.5
*/
public int offsetByCodePoints(int index, int codePointOffset) {
if (index < 0 || index > count) {
throw new IndexOutOfBoundsException();
}
return Character.offsetByCodePointsImpl(value, offset, count,
offset+index, codePointOffset) - offset;
}

/**
* Copy characters from this string into dst starting at dstBegin.
* This method doesn‘t perform any range checking.
*/
void getChars(char dst[], int dstBegin) {
System.arraycopy(value, offset, dst, dstBegin, count);
}

/**
* Copies characters from this string into the destination character
* array.
* 
* The first character to be copied is at index <code>srcBegin</code>;
* the last character to be copied is at index <code>srcEnd-1</code>
* (thus the total number of characters to be copied is
* <code>srcEnd-srcBegin</code>). The characters are copied into the
* subarray of <code>dst</code> starting at index <code>dstBegin</code>
* 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.
* @exception IndexOutOfBoundsException If any of the following
* is true:
* <ul><li><code>srcBegin</code> is negative.
* <li><code>srcBegin</code> is greater than <code>srcEnd</code>
* <li><code>srcEnd</code> is greater than the length of this
* string
* <li><code>dstBegin</code> is negative
* <li><code>dstBegin+(srcEnd-srcBegin)</code> is larger than
* <code>dst.length</code></ul>
*/
public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
if (srcBegin < 0) {
throw new StringIndexOutOfBoundsException(srcBegin);
}
if (srcEnd > count) {
throw new StringIndexOutOfBoundsException(srcEnd);
}
if (srcBegin > srcEnd) {
throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
}
System.arraycopy(value, offset + srcBegin, dst, dstBegin,
srcEnd - srcBegin);
}

/**
* 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 platform‘s 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
public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
if (srcBegin < 0) {
throw new StringIndexOutOfBoundsException(srcBegin);
}
if (srcEnd > count) {
throw new StringIndexOutOfBoundsException(srcEnd);
}
if (srcBegin > srcEnd) {
throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
}
int j = dstBegin;
int n = offset + srcEnd;
int i = offset + srcBegin;
char[] val = value; /* avoid getfield opcode */

while (i < n) {
dst[j++] = (byte)val[i++];
}
}

/**
* 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 JDK1.1
*/
public byte[] getBytes(String charsetName)
throws UnsupportedEncodingException
{
if (charsetName == null) throw new NullPointerException();
return StringCoding.encode(charsetName, value, offset, count);
}

/**
* 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 StringCoding.encode(charset, value, offset, count);
}

/**
* Encodes this {@code String} into a sequence of bytes using the
* platform‘s 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 JDK1.1
*/
public byte[] getBytes() {
return StringCoding.encode(value, offset, count);
}

/**
* 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.
*
* @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;
}
if (anObject instanceof String) {
String anotherString = (String)anObject;
int n = count;
if (n == anotherString.count) {
char v1[] = value;
char v2[] = anotherString.value;
int i = offset;
int j = anotherString.offset;
while (n-- != 0) {
if (v1[i++] != v2[j++])
return false;
}
return true;
}
}
return false;
}

/**
* 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}.
*
* @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) {
synchronized(sb) {
return contentEquals((CharSequence)sb);
}
}

/**
* 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.
*
* @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) {
if (count != cs.length())
return false;
// Argument is a StringBuffer, StringBuilder
if (cs instanceof AbstractStringBuilder) {
char v1[] = value;
char v2[] = ((AbstractStringBuilder)cs).getValue();
int i = offset;
int j = 0;
int n = count;
while (n-- != 0) {
if (v1[i++] != v2[j++])
return false;
}
}
// Argument is a String
if (cs.equals(this))
return true;
// Argument is a generic CharSequence
char v1[] = value;
int i = offset;
int j = 0;
int n = count;
while (n-- != 0) {
if (v1[i++] != cs.charAt(j++))
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 characters in the two strings
* are equal ignoring case.
*
* Two characters {@code c1} and {@code c2} are considered the same
* ignoring case if at least one of the following is true:
* <ul>
* <li> The two characters are the same (as compared by the
* {@code ==} operator)
* <li> Applying the method {@link
* java.lang.Character#toUpperCase(char)} to each character
* produces the same result
* <li> Applying the method {@link
* java.lang.Character#toLowerCase(char)} to each character
* produces the same result
* </ul>
*
* @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)
*/
public boolean equalsIgnoreCase(String anotherString) {
return (this == anotherString) ? true :
(anotherString != null) && (anotherString.count == count) &&
regionMatches(true, 0, anotherString, 0, count);
}

/**
* 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</code> object is compared lexicographically to the
* character sequence represented by the argument string. The result is
* a negative integer if this <code>String</code> object
* lexicographically precedes the argument string. The result is a
* positive integer if this <code>String</code> object lexicographically
* follows the argument string. The result is zero if the strings
* are equal; <code>compareTo</code> returns <code>0</code> exactly when
* the {@link #equals(Object)} method would return <code>true</code>.
* 
* 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 < operator, lexicographically precedes the
* other string. In this case, <code>compareTo</code> returns the
* difference of the two character values at position <code>k</code> 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</code> returns the difference of the lengths of the
* strings -- that is, the value:
* <blockquote><pre>
* this.length()-anotherString.length()
* </pre></blockquote>
*
* @param anotherString the <code>String</code> to be compared.
* @return the value <code>0</code> if the argument string is equal to
* this string; a value less than <code>0</code> if this string
* is lexicographically less than the string argument; and a
* value greater than <code>0</code> if this string is
* lexicographically greater than the string argument.
*/
public int compareTo(String anotherString) {
int len1 = count;
int len2 = anotherString.count;
int n = Math.min(len1, len2);
char v1[] = value;
char v2[] = anotherString.value;
int i = offset;
int j = anotherString.offset;

if (i == j) {
int k = i;
int lim = n + i;
while (k < lim) {
char c1 = v1[k];
char c2 = v2[k];
if (c1 != c2) {
return c1 - c2;
}
k++;
}
} else {
while (n-- != 0) {
char c1 = v1[i++];
char c2 = v2[j++];
if (c1 != c2) {
return c1 - c2;
}
}
}
return len1 - len2;
}

/**
* A Comparator that orders <code>String</code> objects as by
* <code>compareToIgnoreCase</code>. 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 java.text package provides Collators to allow
* locale-sensitive ordering.
*
* @see java.text.Collator#compare(String, String)
* @since 1.2
*/
public static final Comparator<String> CASE_INSENSITIVE_ORDER
= new CaseInsensitiveComparator();
private static class CaseInsensitiveComparator
implements Comparator<String>, java.io.Serializable {
// use serialVersionUID from JDK 1.2.2 for interoperability
private static final long serialVersionUID = 8575799808933029326L;

public int compare(String s1, String s2) {
int n1=s1.length(), n2=s2.length();
for (int i1=0, i2=0; i1<n1 && i2<n2; i1++, i2++) {
char c1 = s1.charAt(i1);
char c2 = s2.charAt(i2);
if (c1 != c2) {
c1 = Character.toUpperCase(c1);
c2 = Character.toUpperCase(c2);
if (c1 != c2) {
c1 = Character.toLowerCase(c1);
c2 = Character.toLowerCase(c2);
if (c1 != c2) {
return c1 - c2;
}
}
}
}
return n1 - n2;
}
}

/**
* Compares two strings lexicographically, ignoring case
* differences. This method returns an integer whose sign is that of
* calling <code>compareTo</code> with normalized versions of the strings
* where case differences have been eliminated by calling
* <code>Character.toLowerCase(Character.toUpperCase(character))</code> on
* each character.
* 
* Note that this method does not take locale into account,
* and will result in an unsatisfactory ordering for certain locales.
* The java.text package provides collators to allow
* locale-sensitive ordering.
*
* @param str the <code>String</code> 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#compare(String, String)
* @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 <tt>String</tt> 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
* <tt>String</tt> object to be compared begins at index <tt>toffset</tt>
* and has length <tt>len</tt>. The substring of other to be compared
* begins at index <tt>ooffset</tt> and has length <tt>len</tt>. The
* result is <tt>false</tt> if and only if at least one of the following
* is true:
* <ul><li><tt>toffset</tt> is negative.
* <li><tt>ooffset</tt> is negative.
* <li><tt>toffset+len</tt> is greater than the length of this
* <tt>String</tt> object.
* <li><tt>ooffset+len</tt> is greater than the length of the other
* argument.
* <li>There is some nonnegative integer k less than <tt>len</tt>
* such that:
* <tt>this.charAt(toffset+k) != other.charAt(ooffset+k)</tt>
* </ul>
*
* @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</code> if the specified subregion of this string
* exactly matches the specified subregion of the string argument;
* <code>false</code> otherwise.
*/
public boolean regionMatches(int toffset, String other, int ooffset,
int len) {
char ta[] = value;
int to = offset + toffset;
char pa[] = other.value;
int po = other.offset + ooffset;
// Note: toffset, ooffset, or len might be near -1>>>1.
if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len)
|| (ooffset > (long)other.count - len)) {
return false;
}
while (len-- > 0) {
if (ta[to++] != pa[po++]) {
return false;
}
}
return true;
}

/**
* Tests if two string regions are equal.
* 
* A substring of this <tt>String</tt> object is compared to a substring
* of the argument <tt>other</tt>. The result is <tt>true</tt> if these
* substrings represent character sequences that are the same, ignoring
* case if and only if <tt>ignoreCase</tt> is true. The substring of
* this <tt>String</tt> object to be compared begins at index
* <tt>toffset</tt> and has length <tt>len</tt>. The substring of
* <tt>other</tt> to be compared begins at index <tt>ooffset</tt> and
* has length <tt>len</tt>. The result is <tt>false</tt> if and only if
* at least one of the following is true:
* <ul><li><tt>toffset</tt> is negative.
* <li><tt>ooffset</tt> is negative.
* <li><tt>toffset+len</tt> is greater than the length of this
* <tt>String</tt> object.
* <li><tt>ooffset+len</tt> is greater than the length of the other
* argument.
* <li><tt>ignoreCase</tt> is <tt>false</tt> and there is some nonnegative
* integer k less than <tt>len</tt> such that:
* <blockquote><pre>
* this.charAt(toffset+k) != other.charAt(ooffset+k)
* </pre></blockquote>
* <li><tt>ignoreCase</tt> is <tt>true</tt> and there is some nonnegative
* integer k less than <tt>len</tt> such that:
* <blockquote><pre>
* Character.toLowerCase(this.charAt(toffset+k)) !=
Character.toLowerCase(other.charAt(ooffset+k))
* </pre></blockquote>
* and:
* <blockquote><pre>
* Character.toUpperCase(this.charAt(toffset+k)) !=
* Character.toUpperCase(other.charAt(ooffset+k))
* </pre></blockquote>
* </ul>
*
* @param ignoreCase if <code>true</code>, 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 to compare.
* @return <code>true</code> if the specified subregion of this string
* matches the specified subregion of the string argument;
* <code>false</code> otherwise. Whether the matching is exact
* or case insensitive depends on the <code>ignoreCase</code>
* argument.
*/
public boolean regionMatches(boolean ignoreCase, int toffset,
String other, int ooffset, int len) {
char ta[] = value;
int to = offset + toffset;
char pa[] = other.value;
int po = other.offset + ooffset;
// Note: toffset, ooffset, or len might be near -1>>>1.
if ((ooffset < 0) || (toffset < 0) || (toffset > (long)count - len) ||
(ooffset > (long)other.count - len)) {
return false;
}
while (len-- > 0) {
char c1 = ta[to++];
char c2 = pa[po++];
if (c1 == c2) {
continue;
}
if (ignoreCase) {
// If characters don‘t match but case may be ignored,
// try converting both characters to uppercase.
// If the results match, then the comparison scan should
// continue.
char u1 = Character.toUpperCase(c1);
char u2 = Character.toUpperCase(c2);
if (u1 == u2) {
continue;
}
// Unfortunately, conversion to uppercase does not work properly
// for the Georgian alphabet, which has strange rules about case
// conversion. So we need to make one last check before
// exiting.
if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
continue;
}
}
return false;
}
return true;
}

/**
* 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</code> if the character sequence represented by the
* argument is a prefix of the substring of this object starting
* at index <code>toffset</code>; <code>false</code> otherwise.
* The result is <code>false</code> if <code>toffset</code> is
* negative or greater than the length of this
* <code>String</code> 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) {
char ta[] = value;
int to = offset + toffset;
char pa[] = prefix.value;
int po = prefix.offset;
int pc = prefix.count;
// Note: toffset might be near -1>>>1.
if ((toffset < 0) || (toffset > count - pc)) {
return false;
}
while (--pc >= 0) {
if (ta[to++] != pa[po++]) {
return false;
}
}
return true;
}

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

/**
* Returns a hash code for this string. The hash code for a
* <code>String</code> object is computed as
* <blockquote><pre>
* s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
* </pre></blockquote>
* using <code>int</code> arithmetic, where <code>s[i]</code> is the
* ith character of the string, <code>n</code> is the length of
* the string, and <code>^</code> indicates exponentiation.
* (The hash value of the empty string is zero.)
*
* @return a hash code value for this object.
*/
public int hashCode() {
int h = hash;
if (h == 0) {
int off = offset;
char val[] = value;
int len = count;

for (int i = 0; i < len; i++) {
h = 31*h + val[off++];
}
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</code> occurs in the character sequence represented by
* this <code>String</code> object, then the index (in Unicode
* code units) of the first such occurrence is returned. For
* values of <code>ch</code> 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</code>, 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</code> 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</code> 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</code> occurs in the
* character sequence represented by this <code>String</code>
* object at an index no smaller than <code>fromIndex</code>, then
* the index of the first such occurrence is returned. For values
* of <code>ch</code> in the range from 0 to 0xFFFF (inclusive),
* this is the smallest value k such that:
* <blockquote><pre>
* (this.charAt(k) == ch) && (k >= fromIndex)
* </pre></blockquote>
* is true. For other values of <code>ch</code>, it is the
* smallest value k such that:
* <blockquote><pre>
* (this.codePointAt(k) == ch) && (k >= fromIndex)
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string at or after position <code>fromIndex</code>, then
* <code>-1</code> is returned.
*
* 
* There is no restriction on the value of <code>fromIndex</code>. 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</code> is returned.
*
* All indices are specified in <code>char</code> 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</code>, or <code>-1</code>
* if the character does not occur.
*/
public int indexOf(int ch, int fromIndex) {
int max = offset + count;
char v[] = value;

if (fromIndex < 0) {
fromIndex = 0;
} else if (fromIndex >= count) {
// Note: fromIndex might be near -1>>>1.
return -1;
}

int i = offset + fromIndex;
if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
// handle most cases here (ch is a BMP code point or a
// negative value (invalid code point))
for (; i < max ; i++) {
if (v[i] == ch) {
return i - offset;
}
}
return -1;
}

if (ch <= Character.MAX_CODE_POINT) {
// handle supplementary characters here
char[] surrogates = Character.toChars(ch);
for (; i < max; i++) {
if (v[i] == surrogates[0]) {
if (i + 1 == max) {
break;
}
if (v[i+1] == surrogates[1]) {
return i - offset;
}
}
}
}
return -1;
}

/**
* Returns the index within this string of the last occurrence of
* the specified character. For values of <code>ch</code> 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</code>, 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</code> is returned. The
* <code>String</code> 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</code> if the character does not occur.
*/
public int lastIndexOf(int ch) {
return lastIndexOf(ch, count - 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</code> in the range
* from 0 to 0xFFFF (inclusive), the index returned is the largest
* value k such that:
* <blockquote><pre>
* (this.charAt(k) == ch) && (k <= fromIndex)
* </pre></blockquote>
* is true. For other values of <code>ch</code>, it is the
* largest value k such that:
* <blockquote><pre>
* (this.codePointAt(k) == ch) && (k <= fromIndex)
* </pre></blockquote>
* is true. In either case, if no such character occurs in this
* string at or before position <code>fromIndex</code>, then
* <code>-1</code> is returned.
*
* All indices are specified in <code>char</code> 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</code>. 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</code>, or <code>-1</code>
* if the character does not occur before that point.
*/
public int lastIndexOf(int ch, int fromIndex) {
int min = offset;
char v[] = value;

int i = offset + ((fromIndex >= count) ? count - 1 : fromIndex);

if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
// handle most cases here (ch is a BMP code point or a
// negative value (invalid code point))
for (; i >= min ; i--) {
if (v[i] == ch) {
return i - offset;
}
}
return -1;
}

int max = offset + count;
if (ch <= Character.MAX_CODE_POINT) {
// handle supplementary characters here
char[] surrogates = Character.toChars(ch);
for (; i >= min; i--) {
if (v[i] == surrogates[0]) {
if (i + 1 == max) {
break;
}
if (v[i+1] == surrogates[1]) {
return i - offset;
}
}
}
}
return -1;
}

/**
* Returns the index within this string of the first occurrence of the
* specified substring. The integer returned is the smallest value
* k such that:
* <blockquote><pre>
* this.startsWith(str, k)
* </pre></blockquote>
* is <code>true</code>.
*
* @param str any string.
* @return if the string argument occurs as a substring within this
* object, then the index of the first character of the first
* such substring is returned; if it does not occur as a
* substring, <code>-1</code> is returned.
*/
public int indexOf(String str) {
return indexOf(str, 0);
}

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

/**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int indexOf(char[] source, int sourceOffset, int sourceCount,
char[] target, int targetOffset, int targetCount,
int fromIndex) {
if (fromIndex >= sourceCount) {
return (targetCount == 0 ? sourceCount : -1);
}
if (fromIndex < 0) {
fromIndex = 0;
}
if (targetCount == 0) {
return fromIndex;
}

char first = target[targetOffset];
int max = sourceOffset + (sourceCount - targetCount);

for (int i = sourceOffset + fromIndex; i <= max; i++) {
/* Look for first character. */
if (source[i] != first) {
while (++i <= max && source[i] != first);
}

/* Found first character, now look at the rest of v2 */
if (i <= max) {
int j = i + 1;
int end = j + targetCount - 1;
for (int k = targetOffset + 1; j < end && source[j] ==
target[k]; j++, k++);

if (j == end) {
/* Found whole string. */
return i - sourceOffset;
}
}
}
return -1;
}

/**
* Returns the index within this string of the rightmost occurrence
* of the specified substring. The rightmost empty string "" is
* considered to occur at the index value <code>this.length()</code>.
* The returned index is the largest value k such that
* <blockquote><pre>
* this.startsWith(str, k)
* </pre></blockquote>
* is true.
*
* @param str the substring to search for.
* @return if the string argument occurs one or more times as a substring
* within this object, then the index of the first character of
* the last such substring is returned. If it does not occur as
* a substring, <code>-1</code> is returned.
*/
public int lastIndexOf(String str) {
return lastIndexOf(str, count);
}

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

/**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,
char[] target, int targetOffset, int targetCount,
int fromIndex) {
/*
* Check arguments; return immediately where possible. For
* consistency, don‘t check for null str.
*/
int rightIndex = sourceCount - targetCount;
if (fromIndex < 0) {
return -1;
}
if (fromIndex > rightIndex) {
fromIndex = rightIndex;
}
/* Empty string always matches. */
if (targetCount == 0) {
return fromIndex;
}

int strLastIndex = targetOffset + targetCount - 1;
char strLastChar = target[strLastIndex];
int min = sourceOffset + targetCount - 1;
int i = min + fromIndex;

startSearchForLastChar:
while (true) {
while (i >= min && source[i] != strLastChar) {
i--;
}
if (i < min) {
return -1;
}
int j = i - 1;
int start = j - (targetCount - 1);
int k = strLastIndex - 1;

while (j > start) {
if (source[j--] != target[k--]) {
i--;
continue startSearchForLastChar;
}
}
return start - sourceOffset + 1;
}
}

/**
* Returns a new 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.
* @exception IndexOutOfBoundsException if
* <code>beginIndex</code> is negative or larger than the
* length of this <code>String</code> object.
*/
public String substring(int beginIndex) {
return substring(beginIndex, count);
}

/**
* Returns a new string that is a substring of this string. The
* substring begins at the specified <code>beginIndex</code> and
* extends to the character at index <code>endIndex - 1</code>.
* Thus the length of the substring is <code>endIndex-beginIndex</code>.
* 
* 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.
* @exception IndexOutOfBoundsException if the
* <code>beginIndex</code> is negative, or
* <code>endIndex</code> is larger than the length of
* this <code>String</code> object, or
* <code>beginIndex</code> is larger than
* <code>endIndex</code>.
*/
public String substring(int beginIndex, int endIndex) {
if (beginIndex < 0) {
throw new StringIndexOutOfBoundsException(beginIndex);
}
if (endIndex > count) {
throw new StringIndexOutOfBoundsException(endIndex);
}
if (beginIndex > endIndex) {
throw new StringIndexOutOfBoundsException(endIndex - beginIndex);
}
return ((beginIndex == 0) && (endIndex == count)) ? this :
new String(offset + beginIndex, endIndex - beginIndex, value);
}

/**
* Returns a new 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>
*
* This method is defined so that the <tt>String</tt> 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 <tt>beginIndex</tt> or <tt>endIndex</tt> are negative,
* if <tt>endIndex</tt> is greater than <tt>length()</tt>,
* or if <tt>beginIndex</tt> is greater than <tt>startIndex</tt>
*
* @since 1.4
* @spec JSR-51
*/
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</code>, then this
* <code>String</code> object is returned. Otherwise, a new
* <code>String</code> object is created, representing a character
* sequence that is the concatenation of the character sequence
* represented by this <code>String</code> 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</code> that is concatenated to the end
* of this <code>String</code>.
* @return a string that represents the concatenation of this object‘s
* characters followed by the string argument‘s characters.
*/
public String concat(String str) {
int otherLen = str.length();
if (otherLen == 0) {
return this;
}
char buf[] = new char[count + otherLen];
getChars(0, count, buf, 0);
str.getChars(0, otherLen, buf, count);
return new String(0, count + otherLen, buf);
}

/**
* Returns a new string resulting from replacing all occurrences of
* <code>oldChar</code> in this string with <code>newChar</code>.
* 
* If the character <code>oldChar</code> does not occur in the
* character sequence represented by this <code>String</code> object,
* then a reference to this <code>String</code> object is returned.
* Otherwise, a new <code>String</code> object is created that
* represents a character sequence identical to the character sequence
* represented by this <code>String</code> object, except that every
* occurrence of <code>oldChar</code> is replaced by an occurrence
* of <code>newChar</code>.
* 
* 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</code> with <code>newChar</code>.
*/
public String replace(char oldChar, char newChar) {
if (oldChar != newChar) {
int len = count;
int i = -1;
char[] val = value; /* avoid getfield opcode */
int off = offset; /* avoid getfield opcode */

while (++i < len) {
if (val[off + i] == oldChar) {
break;
}
}
if (i < len) {
char buf[] = new char[len];
for (int j = 0 ; j < i ; j++) {
buf[j] = val[off+j];
}
while (i < len) {
char c = val[off + i];
buf[i] = (c == oldChar) ? newChar : c;
i++;
}
return new String(0, len, buf);
}
}
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<tt>.matches(</tt>regex<tt>)</tt> yields exactly the
* same result as the expression
*
* <blockquote><tt> {@link java.util.regex.Pattern}.{@link
* java.util.regex.Pattern#matches(String,CharSequence)
* matches}(</tt>regex<tt>,</tt> str<tt>)</tt></blockquote>
*
* @param regex
* the regular expression to which this string is to be matched
*
* @return <tt>true</tt> 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
* @spec JSR-51
*/
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</code>, false otherwise
* @throws NullPointerException if <code>s</code> is <code>null</code>
* @since 1.5
*/
public boolean contains(CharSequence s) {
return indexOf(s.toString()) > -1;
}

/**
* 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<tt>.replaceFirst(</tt>regex<tt>,</tt> repl<tt>)</tt>
* yields exactly the same result as the expression
*
* <blockquote><tt>
* {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
* compile}(</tt>regex<tt>).{@link
* java.util.regex.Pattern#matcher(java.lang.CharSequence)
* matcher}(</tt>str<tt>).{@link java.util.regex.Matcher#replaceFirst
* replaceFirst}(</tt>repl<tt>)</tt></blockquote>
*
*
* Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) 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 <tt>String</tt>
*
* @throws PatternSyntaxException
* if the regular expression‘s syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
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<tt>.replaceAll(</tt>regex<tt>,</tt> repl<tt>)</tt>
* yields exactly the same result as the expression
*
* <blockquote><tt>
* {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
* compile}(</tt>regex<tt>).{@link
* java.util.regex.Pattern#matcher(java.lang.CharSequence)
* matcher}(</tt>str<tt>).{@link java.util.regex.Matcher#replaceAll
* replaceAll}(</tt>repl<tt>)</tt></blockquote>
*
*
* Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) 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 <tt>String</tt>
*
* @throws PatternSyntaxException
* if the regular expression‘s syntax is invalid
*
* @see java.util.regex.Pattern
*
* @since 1.4
* @spec JSR-51
*/
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
* @throws NullPointerException if <code>target</code> or
* <code>replacement</code> is <code>null</code>.
* @since 1.5
*/
public String replace(CharSequence target, CharSequence replacement) {
return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
this).replaceAll(Matcher.quoteReplacement(replacement.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.
*
* The <tt>limit</tt> parameter controls the number of times the
* pattern is applied and therefore affects the length of the resulting
* array. If the limit n is greater than zero then the pattern
* will be applied at most n - 1 times, the array‘s
* length will be no greater than n, and the array‘s last entry
* will contain all input beyond the last matched delimiter. If n
* is non-positive then the pattern will be applied as many times as
* possible and the array can have any length. If n 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.
*
* The string <tt>"boo:and:foo"</tt>, for example, yields the
* following results with these parameters:
*
* <blockquote><table cellpadding=1 cellspacing=0 summary="Split example showing regex, limit, and result">
* <tr>
* <th>Regex</th>
* <th>Limit</th>
* <th>Result</th>
* </tr>
* <tr><td align=center>:</td>
* <td align=center>2</td>
* <td><tt>{ "boo", "and:foo" }</tt></td></tr>
* <tr><td align=center>:</td>
* <td align=center>5</td>
* <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
* <tr><td align=center>:</td>
* <td align=center>-2</td>
* <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
* <tr><td align=center>o</td>
* <td align=center>5</td>
* <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
* <tr><td align=center>o</td>
* <td align=center>-2</td>
* <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
* <tr><td align=center>o</td>
* <td align=center>0</td>
* <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
* </table></blockquote>
*
* An invocation of this method of the form
* str.<tt>split(</tt>regex<tt>,</tt> n<tt>)</tt>
* yields the same result as the expression
*
* <blockquote>
* {@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile
* compile}<tt>(</tt>regex<tt>)</tt>.{@link
* java.util.regex.Pattern#split(java.lang.CharSequence,int)
* split}<tt>(</tt>str<tt>,</tt> n<tt>)</tt>
* </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
* @spec JSR-51
*/
public String[] split(String regex, int limit) {
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 <tt>"boo:and:foo"</tt>, for example, yields the following
* results with these expressions:
*
* <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
* <tr>
* <th>Regex</th>
* <th>Result</th>
* </tr>
* <tr><td align=center>:</td>
* <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
* <tr><td align=center>o</td>
* <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
* </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
* @spec JSR-51
*/
public String[] split(String regex) {
return split(regex, 0);
}

/**
* Converts all of the characters in this <code>String</code> to lower
* case using the rules of the given <code>Locale</code>. 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</code> may be a different length than the original <code>String</code>.
* 
* Examples of lowercase mappings are in the following table:
* <table border="1" summary="Lowercase mapping examples showing language code of locale, upper case, lower case, and description">
* <tr>
* <th>Language Code of Locale</th>
* <th>Upper Case</th>
* <th>Lower Case</th>
* <th>Description</th>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0130</td>
* <td>\u0069</td>
* <td>capital letter I with dot above -> small letter i</td>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0049</td>
* <td>\u0131</td>
* <td>capital letter I -> small letter dotless i </td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>French Fries</td>
* <td>french fries</td>
* <td>lowercased all chars in String</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td><img src="doc-files/capiota.gif" alt="capiota"><img src="doc-files/capchi.gif" alt="capchi">
* <img src="doc-files/captheta.gif" alt="captheta"><img src="doc-files/capupsil.gif" alt="capupsil">
* <img src="doc-files/capsigma.gif" alt="capsigma"></td>
* <td><img src="doc-files/iota.gif" alt="iota"><img src="doc-files/chi.gif" alt="chi">
* <img src="doc-files/theta.gif" alt="theta"><img src="doc-files/upsilon.gif" alt="upsilon">
* <img src="doc-files/sigma1.gif" alt="sigma"></td>
* <td>lowercased all chars in String</td>
* </tr>
* </table>
*
* @param locale use the case transformation rules for this locale
* @return the <code>String</code>, 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) {
if (locale == null) {
throw new NullPointerException();
}

int firstUpper;

/* Now check if there are any characters that need to be changed. */
scan: {
for (firstUpper = 0 ; firstUpper < count; ) {
char c = value[offset+firstUpper];
if ((c >= Character.MIN_HIGH_SURROGATE) &&
(c <= Character.MAX_HIGH_SURROGATE)) {
int supplChar = codePointAt(firstUpper);
if (supplChar != Character.toLowerCase(supplChar)) {
break scan;
}
firstUpper += Character.charCount(supplChar);
} else {
if (c != Character.toLowerCase(c)) {
break scan;
}
firstUpper++;
}
}
return this;
}

char[] result = new char[count];
int resultOffset = 0; /* result may grow, so i+resultOffset
* is the write location in result */

/* Just copy the first few lowerCase characters. */
System.arraycopy(value, offset, result, 0, firstUpper);

String lang = locale.getLanguage();
boolean localeDependent =
(lang == "tr" || lang == "az" || lang == "lt");
char[] lowerCharArray;
int lowerChar;
int srcChar;
int srcCount;
for (int i = firstUpper; i < count; i += srcCount) {
srcChar = (int)value[offset+i];
if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
(char)srcChar <= Character.MAX_HIGH_SURROGATE) {
srcChar = codePointAt(i);
srcCount = Character.charCount(srcChar);
} else {
srcCount = 1;
}
if (localeDependent || srcChar == ‘\u03A3‘) { // GREEK CAPITAL LETTER SIGMA
lowerChar = ConditionalSpecialCasing.toLowerCaseEx(this, i, locale);
} else {
lowerChar = Character.toLowerCase(srcChar);
}
if ((lowerChar == Character.ERROR) ||
(lowerChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
if (lowerChar == Character.ERROR) {
lowerCharArray =
ConditionalSpecialCasing.toLowerCaseCharArray(this, i, locale);
} else if (srcCount == 2) {
resultOffset += Character.toChars(lowerChar, result, i + resultOffset) - srcCount;
continue;
} else {
lowerCharArray = Character.toChars(lowerChar);
}

/* Grow result if needed */
int mapLen = lowerCharArray.length;
if (mapLen > srcCount) {
char[] result2 = new char[result.length + mapLen - srcCount];
System.arraycopy(result, 0, result2, 0,
i + resultOffset);
result = result2;
}
for (int x=0; x<mapLen; ++x) {
result[i+resultOffset+x] = lowerCharArray[x];
}
resultOffset += (mapLen - srcCount);
} else {
result[i+resultOffset] = (char)lowerChar;
}
}
return new String(0, count+resultOffset, result);
}

/**
* Converts all of the characters in this <code>String</code> to lower
* case using the rules of the default locale. This is equivalent to calling
* <code>toLowerCase(Locale.getDefault())</code>.
* 
* 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()</code> in a Turkish locale
* returns <code>"t\u0131tle"</code>, where ‘\u0131‘ is the LATIN SMALL
* LETTER DOTLESS I character.
* To obtain correct results for locale insensitive strings, use
* <code>toLowerCase(Locale.ENGLISH)</code>.
* 
* @return the <code>String</code>, 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</code> to upper
* case using the rules of the given <code>Locale</code>. 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</code> may be a different length than the original <code>String</code>.
* 
* Examples of locale-sensitive and 1:M case mappings are in the following table.
* 
* <table border="1" summary="Examples of locale-sensitive and 1:M case mappings. Shows Language code of locale, lower case, upper case, and description.">
* <tr>
* <th>Language Code of Locale</th>
* <th>Lower Case</th>
* <th>Upper Case</th>
* <th>Description</th>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0069</td>
* <td>\u0130</td>
* <td>small letter i -> capital letter I with dot above</td>
* </tr>
* <tr>
* <td>tr (Turkish)</td>
* <td>\u0131</td>
* <td>\u0049</td>
* <td>small letter dotless i -> capital letter I</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>\u00df</td>
* <td>\u0053 \u0053</td>
* <td>small letter sharp s -> two letters: SS</td>
* </tr>
* <tr>
* <td>(all)</td>
* <td>Fahrvergnügen</td>
* <td>FAHRVERGNÜGEN</td>
* <td></td>
* </tr>
* </table>
* @param locale use the case transformation rules for this locale
* @return the <code>String</code>, 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) {
if (locale == null) {
throw new NullPointerException();
}

int firstLower;

/* Now check if there are any characters that need to be changed. */
scan: {
for (firstLower = 0 ; firstLower < count; ) {
int c = (int)value[offset+firstLower];
int srcCount;
if ((c >= Character.MIN_HIGH_SURROGATE) &&
(c <= Character.MAX_HIGH_SURROGATE)) {
c = codePointAt(firstLower);
srcCount = Character.charCount(c);
} else {
srcCount = 1;
}
int upperCaseChar = Character.toUpperCaseEx(c);
if ((upperCaseChar == Character.ERROR) ||
(c != upperCaseChar)) {
break scan;
}
firstLower += srcCount;
}
return this;
}

char[] result = new char[count]; /* may grow */
int resultOffset = 0; /* result may grow, so i+resultOffset
* is the write location in result */

/* Just copy the first few upperCase characters. */
System.arraycopy(value, offset, result, 0, firstLower);

String lang = locale.getLanguage();
boolean localeDependent =
(lang == "tr" || lang == "az" || lang == "lt");
char[] upperCharArray;
int upperChar;
int srcChar;
int srcCount;
for (int i = firstLower; i < count; i += srcCount) {
srcChar = (int)value[offset+i];
if ((char)srcChar >= Character.MIN_HIGH_SURROGATE &&
(char)srcChar <= Character.MAX_HIGH_SURROGATE) {
srcChar = codePointAt(i);
srcCount = Character.charCount(srcChar);
} else {
srcCount = 1;
}
if (localeDependent) {
upperChar = ConditionalSpecialCasing.toUpperCaseEx(this, i, locale);
} else {
upperChar = Character.toUpperCaseEx(srcChar);
}
if ((upperChar == Character.ERROR) ||
(upperChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
if (upperChar == Character.ERROR) {
if (localeDependent) {
upperCharArray =
ConditionalSpecialCasing.toUpperCaseCharArray(this, i, locale);
} else {
upperCharArray = Character.toUpperCaseCharArray(srcChar);
}
} else if (srcCount == 2) {
resultOffset += Character.toChars(upperChar, result, i + resultOffset) - srcCount;
continue;
} else {
upperCharArray = Character.toChars(upperChar);
}

/* Grow result if needed */
int mapLen = upperCharArray.length;
if (mapLen > srcCount) {
char[] result2 = new char[result.length + mapLen - srcCount];
System.arraycopy(result, 0, result2, 0,
i + resultOffset);
result = result2;
}
for (int x=0; x<mapLen; ++x) {
result[i+resultOffset+x] = upperCharArray[x];
}
resultOffset += (mapLen - srcCount);
} else {
result[i+resultOffset] = (char)upperChar;
}
}
return new String(0, count+resultOffset, result);
}

/**
* Converts all of the characters in this <code>String</code> to upper
* case using the rules of the default locale. This method is equivalent to
* <code>toUpperCase(Locale.getDefault())</code>.
* 
* 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()</code> in a Turkish locale
* returns <code>"T\u0130TLE"</code>, where ‘\u0130‘ is the LATIN CAPITAL
* LETTER I WITH DOT ABOVE character.
* To obtain correct results for locale insensitive strings, use
* <code>toUpperCase(Locale.ENGLISH)</code>.
* 
* @return the <code>String</code>, converted to uppercase.
* @see java.lang.String#toUpperCase(Locale)
*/
public String toUpperCase() {
return toUpperCase(Locale.getDefault());
}

/**
* Returns a copy of the string, with leading and trailing whitespace
* omitted.
* 
* If this <code>String</code> object represents an empty character
* sequence, or the first and last characters of character sequence
* represented by this <code>String</code> object both have codes
* greater than <code>‘\u0020‘</code> (the space character), then a
* reference to this <code>String</code> object is returned.
* 
* Otherwise, if there is no character with a code greater than
* <code>‘\u0020‘</code> in the string, then a new
* <code>String</code> object representing an empty string is created
* and returned.
* 
* Otherwise, let k be the index of the first character in the
* string whose code is greater than <code>‘\u0020‘</code>, and let
* m be the index of the last character in the string whose code
* is greater than <code>‘\u0020‘</code>. A new <code>String</code>
* object is created, 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)</code>.
* 
* This method may be used to trim whitespace (as defined above) from
* the beginning and end of a string.
*
* @return A copy of this string with leading and trailing white
* space removed, or this string if it has no leading or
* trailing white space.
*/
public String trim() {
int len = count;
int st = 0;
int off = offset; /* avoid getfield opcode */
char[] val = value; /* avoid getfield opcode */

while ((st < len) && (val[off + st] <= ‘ ‘)) {
st++;
}
while ((st < len) && (val[off + len - 1] <= ‘ ‘)) {
len--;
}
return ((st > 0) || (len < count)) ? substring(st, len) : this;
}

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

/**
* 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() {
char result[] = new char[count];
getChars(0, count, result, 0);
return result;
}

/**
* 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() Locale.getDefault()}.
*
* @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
* the <a href="http://java.sun.com/docs/books/vmspec/">Java
* Virtual Machine Specification</a>. The behaviour on a
* <tt>null</tt> argument depends on the <a
* href="../util/Formatter.html#syntax">conversion</a>.
*
* @throws 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.
*
* @throws NullPointerException
* If the <tt>format</tt> is <tt>null</tt>
*
* @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 <tt>l</tt> is <tt>null</tt> 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
* the <a href="http://java.sun.com/docs/books/vmspec/">Java
* Virtual Machine Specification</a>. The behaviour on a
* <tt>null</tt> argument depends on the <a
* href="../util/Formatter.html#syntax">conversion</a>.
*
* @throws 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
*
* @throws NullPointerException
* If the <tt>format</tt> is <tt>null</tt>
*
* @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();
}

/**
* Returns the string representation of the <code>Object</code> argument.
*
* @param obj an <code>Object</code>.
* @return if the argument is <code>null</code>, then a string equal to
* <code>"null"</code>; otherwise, the value of
* <code>obj.toString()</code> 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</code> array
* argument. The contents of the character array are copied; subsequent
* modification of the character array does not affect the newly
* created string.
*
* @param data a <code>char</code> array.
* @return a newly allocated string representing the same sequence of
* characters contained in the character array argument.
*/
public static String valueOf(char data[]) {
return new String(data);
}

/**
* Returns the string representation of a specific subarray of the
* <code>char</code> array argument.
* 
* The <code>offset</code> argument is the index of the first
* character of the subarray. The <code>count</code> 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 data the character array.
* @param offset the initial offset into the value of the
* <code>String</code>.
* @param count the length of the value of the <code>String</code>.
* @return a string representing the sequence of characters contained
* in the subarray of the character array argument.
* @exception IndexOutOfBoundsException if <code>offset</code> is
* negative, or <code>count</code> is negative, or
* <code>offset+count</code> is larger than
* <code>data.length</code>.
*/
public static String valueOf(char data[], int offset, int count) {
return new String(data, offset, count);
}

/**
* Returns a String that represents the character sequence in the
* array specified.
*
* @param data the character array.
* @param offset initial offset of the subarray.
* @param count length of the subarray.
* @return a <code>String</code> that contains the characters of the
* specified subarray of the character array.
*/
public static String copyValueOf(char data[], int offset, int count) {
// All public String constructors now copy the data.
return new String(data, offset, count);
}

/**
* Returns a String that represents the character sequence in the
* array specified.
*
* @param data the character array.
* @return a <code>String</code> that contains the characters of the
* character array.
*/
public static String copyValueOf(char data[]) {
return copyValueOf(data, 0, data.length);
}

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

/**
* Returns the string representation of the <code>char</code>
* argument.
*
* @param c a <code>char</code>.
* @return a string of length <code>1</code> containing
* as its single character the argument <code>c</code>.
*/
public static String valueOf(char c) {
char data[] = {c};
return new String(0, 1, data);
}

/**
* Returns the string representation of the <code>int</code> argument.
* 
* The representation is exactly the one returned by the
* <code>Integer.toString</code> method of one argument.
*
* @param i an <code>int</code>.
* @return a string representation of the <code>int</code> argument.
* @see java.lang.Integer#toString(int, int)
*/
public static String valueOf(int i) {
return Integer.toString(i, 10);
}

/**
* Returns the string representation of the <code>long</code> argument.
* 
* The representation is exactly the one returned by the
* <code>Long.toString</code> method of one argument.
*
* @param l a <code>long</code>.
* @return a string representation of the <code>long</code> argument.
* @see java.lang.Long#toString(long)
*/
public static String valueOf(long l) {
return Long.toString(l, 10);
}

/**
* Returns the string representation of the <code>float</code> argument.
* 
* The representation is exactly the one returned by the
* <code>Float.toString</code> method of one argument.
*
* @param f a <code>float</code>.
* @return a string representation of the <code>float</code> 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</code> argument.
* 
* The representation is exactly the one returned by the
* <code>Double.toString</code> method of one argument.
*
* @param d a <code>double</code>.
* @return a string representation of the <code>double</code> 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</code>.
* 
* When the intern method is invoked, if the pool already contains a
* string equal to this <code>String</code> object as determined by
* the {@link #equals(Object)} method, then the string from the pool is
* returned. Otherwise, this <code>String</code> object is added to the
* pool and a reference to this <code>String</code> object is returned.
* 
* It follows that for any two strings <code>s</code> and <code>t</code>,
* <code>s.intern() == t.intern()</code> is <code>true</code>
* if and only if <code>s.equals(t)</code> is <code>true</code>.
* 
* All literal strings and string-valued constant expressions are
* interned. String literals are defined in §3.10.5 of the
* <a href="http://java.sun.com/docs/books/jls/html/">Java Language
* Specification</a>
*
* @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();

}

深入Java—String源代码

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原文地址：http://www.cnblogs.com/harderman-mapleleaves/p/4353287.html

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