String

一：String

字符：Java中用char类型来表示 数字、字母、标点符号等。Java用两个字节存储一个字符。字符从本质上讲是数字，每个字符都可以映射到一个正整数。
字符串：表示固定长度的字符序列。字符串对象是不能改变的。

二：源代码

public final class String implements java.io.Serializable, Comparable<String>, CharSequence {    /** 用char数组来存储String*/    private final char value[];    /** 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 into an ObjectOutputStream according to     * <a href="{@docRoot}/../platform/serialization/spec/output.html">     * Object Serialization Specification, Section 6.2, "Stream Elements"</a>     */    private static final ObjectStreamField[] serialPersistentFields =        new ObjectStreamField[0];    /**     *  String s = new String() 创建空的char数组     */    public String() {        this.value = new char[0];    }    /**     *  String s = new String("aaaa")     */    public String(String original) {        this.value = original.value;        this.hash = original.hash;    }    /**     * 将value保存到本地     */    public String(char value[]) {        this.value = Arrays.copyOf(value, value.length);    }    /**     *      */    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.value = Arrays.copyOfRange(value, offset, offset+count);    }    /**     */    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);        }        final int end = offset + count;        // Pass 1: Compute precise size of char[]        int n = count;        for (int i = offset; i < end; i++) {            int c = codePoints[i];            if (Character.isBmpCodePoint(c))                continue;            else if (Character.isValidCodePoint(c))                n++;            else throw new IllegalArgumentException(Integer.toString(c));        }        // Pass 2: Allocate and fill in char[]        final char[] v = new char[n];        for (int i = offset, j = 0; i < end; i++, j++) {            int c = codePoints[i];            if (Character.isBmpCodePoint(c))                v[j] = (char)c;            else                Character.toSurrogates(c, v, j++);        }        this.value = v;    }    /**     */    @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.value = value;    }    /**     */    @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);    }    /**     */    public String(byte bytes[], int offset, int length, String charsetName)            throws UnsupportedEncodingException {        if (charsetName == null)            throw new NullPointerException("charsetName");        checkBounds(bytes, offset, length);        this.value = StringCoding.decode(charsetName, bytes, offset, length);    }    /**     */    public String(byte bytes[], int offset, int length, Charset charset) {        if (charset == null)            throw new NullPointerException("charset");        checkBounds(bytes, offset, length);        this.value =  StringCoding.decode(charset, bytes, offset, length);    }    /**     */    public String(byte bytes[], String charsetName)            throws UnsupportedEncodingException {        this(bytes, 0, bytes.length, charsetName);    }    /**     */    public String(byte bytes[], Charset charset) {        this(bytes, 0, bytes.length, charset);    }    /**     */    public String(byte bytes[], int offset, int length) {        checkBounds(bytes, offset, length);        this.value = StringCoding.decode(bytes, offset, length);    }    /**     */    public String(byte bytes[]) {        this(bytes, 0, bytes.length);    }    /**     * 线程安全的     */    public String(StringBuffer buffer) {        synchronized(buffer) {            this.value = Arrays.copyOf(buffer.getValue(), buffer.length());        }    }    /**     */    public String(StringBuilder builder) {        this.value = Arrays.copyOf(builder.getValue(), builder.length());    }    /*    * Package private constructor which shares value array for speed.    * this constructor is always expected to be called with share==true.    * a separate constructor is needed because we already have a public    * String(char[]) constructor that makes a copy of the given char[].    */    String(char[] value, boolean share) {        // assert share : "unshared not supported";        this.value = value;    }    /**     * 字符串长度     */    public int length() {        return value.length;    }    /**     * 是否是空字符 ""     */    public boolean isEmpty() {        return value.length == 0;    }    /**     *  当前char数组  获取对应索引的字符     */    public char charAt(int index) {        if ((index < 0) || (index >= value.length)) {            throw new StringIndexOutOfBoundsException(index);        }        return value[index];    }    /**     *  当前char数组  获取对应索引的字符对应的Unicode值      */    public int codePointAt(int index) {        if ((index < 0) || (index >= value.length)) {            throw new StringIndexOutOfBoundsException(index);        }        return Character.codePointAtImpl(value, index, value.length);    }    /**     * 当前char数组  获取对应索引之前的字符对应的Unicode值      */    public int codePointBefore(int index) {        int i = index - 1;        if ((i < 0) || (i >= value.length)) {            throw new StringIndexOutOfBoundsException(index);        }        return Character.codePointBeforeImpl(value, index, 0);    }    /**     */    public int codePointCount(int beginIndex, int endIndex) {        if (beginIndex < 0 || endIndex > value.length || beginIndex > endIndex) {            throw new IndexOutOfBoundsException();        }        return Character.codePointCountImpl(value, beginIndex, endIndex - beginIndex);    }    /**     */    public int offsetByCodePoints(int index, int codePointOffset) {        if (index < 0 || index > value.length) {            throw new IndexOutOfBoundsException();        }        return Character.offsetByCodePointsImpl(value, 0, value.length,                index, codePointOffset);    }    /**     * This method doesn't perform any range checking.     */    void getChars(char dst[], int dstBegin) {        System.arraycopy(value, 0, dst, dstBegin, value.length);    }    /**     */    public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {        if (srcBegin < 0) {            throw new StringIndexOutOfBoundsException(srcBegin);        }        if (srcEnd > value.length) {            throw new StringIndexOutOfBoundsException(srcEnd);        }        if (srcBegin > srcEnd) {            throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);        }        System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);    }    /**     */    @Deprecated    public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {        if (srcBegin < 0) {            throw new StringIndexOutOfBoundsException(srcBegin);        }        if (srcEnd > value.length) {            throw new StringIndexOutOfBoundsException(srcEnd);        }        if (srcBegin > srcEnd) {            throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);        }        Objects.requireNonNull(dst);        int j = dstBegin;        int n = srcEnd;        int i = srcBegin;        char[] val = value;   /* avoid getfield opcode */        while (i < n) {            dst[j++] = (byte)val[i++];        }    }    /**     * 使用给定的 charset 将此 String 编码到 byte 序列，并将结果存储到新的 byte 数组     */    public byte[] getBytes(String charsetName)            throws UnsupportedEncodingException {        if (charsetName == null) throw new NullPointerException();        return StringCoding.encode(charsetName, value, 0, value.length);    }    /**     */    public byte[] getBytes(Charset charset) {        if (charset == null) throw new NullPointerException();        return StringCoding.encode(charset, value, 0, value.length);    }    /**     * 使用默认的 charset 将此 String 编码到 byte 序列，并将结果存储到新的 byte 数组     */    public byte[] getBytes() {        return StringCoding.encode(value, 0, value.length);    }    /**     * 字符串内容比较     */    public boolean equals(Object anObject) {        if (this == anObject) {            return true;        }        if (anObject instanceof String) {            String anotherString = (String)anObject;            int n = value.length;            if (n == anotherString.value.length) {                char v1[] = value;                char v2[] = anotherString.value;                int i = 0;                while (n-- != 0) {                    if (v1[i] != v2[i])                        return false;                    i++;                }                return true;            }        }        return false;    }    /**     */    public boolean contentEquals(StringBuffer sb) {        return contentEquals((CharSequence)sb);    }    private boolean nonSyncContentEquals(AbstractStringBuilder sb) {        char v1[] = value;        char v2[] = sb.getValue();        int n = v1.length;        if (n != sb.length()) {            return false;        }        for (int i = 0; i < n; i++) {            if (v1[i] != v2[i]) {                return false;            }        }        return true;    }    /**     */    public boolean contentEquals(CharSequence cs) {        // Argument is a StringBuffer, StringBuilder        if (cs instanceof AbstractStringBuilder) {            if (cs instanceof StringBuffer) {                synchronized(cs) {                   return nonSyncContentEquals((AbstractStringBuilder)cs);                }            } else {                return nonSyncContentEquals((AbstractStringBuilder)cs);            }        }        // Argument is a String        if (cs instanceof String) {            return equals(cs);        }        // Argument is a generic CharSequence        char v1[] = value;        int n = v1.length;        if (n != cs.length()) {            return false;        }        for (int i = 0; i < n; i++) {            if (v1[i] != cs.charAt(i)) {                return false;            }        }        return true;    }    /**     */    public boolean equalsIgnoreCase(String anotherString) {        return (this == anotherString) ? true                : (anotherString != null)                && (anotherString.value.length == value.length)                && regionMatches(true, 0, anotherString, 0, value.length);    }    /**     */    public int compareTo(String anotherString) {        int len1 = value.length;        int len2 = anotherString.value.length;        int lim = Math.min(len1, len2);        char v1[] = value;        char v2[] = anotherString.value;        int k = 0;        while (k < lim) {            char c1 = v1[k];            char c2 = v2[k];            if (c1 != c2) {                return c1 - c2;            }            k++;        }        return len1 - len2;    }    /**     */    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();            int n2 = s2.length();            int min = Math.min(n1, n2);            for (int i = 0; i < min; i++) {                char c1 = s1.charAt(i);                char c2 = s2.charAt(i);                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) {                            // No overflow because of numeric promotion                            return c1 - c2;                        }                    }                }            }            return n1 - n2;        }        /** Replaces the de-serialized object. */        private Object readResolve() { return CASE_INSENSITIVE_ORDER; }    }    /**     */    public int compareToIgnoreCase(String str) {        return CASE_INSENSITIVE_ORDER.compare(this, str);    }    /**     */    public boolean regionMatches(int toffset, String other, int ooffset,            int len) {        char ta[] = value;        int to = toffset;        char pa[] = other.value;        int po = ooffset;        // Note: toffset, ooffset, or len might be near -1>>>1.        if ((ooffset < 0) || (toffset < 0)                || (toffset > (long)value.length - len)                || (ooffset > (long)other.value.length - len)) {            return false;        }        while (len-- > 0) {            if (ta[to++] != pa[po++]) {                return false;            }        }        return true;    }    /**     */    public boolean regionMatches(boolean ignoreCase, int toffset,            String other, int ooffset, int len) {        char ta[] = value;        int to = toffset;        char pa[] = other.value;        int po = ooffset;        // Note: toffset, ooffset, or len might be near -1>>>1.        if ((ooffset < 0) || (toffset < 0)                || (toffset > (long)value.length - len)                || (ooffset > (long)other.value.length - 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;    }    /**     *  测试此字符串是否以指定的前缀开始     */    public boolean startsWith(String prefix, int toffset) {        char ta[] = value;        int to = toffset;        char pa[] = prefix.value;        int po = 0;        int pc = prefix.value.length;        // Note: toffset might be near -1>>>1.        if ((toffset < 0) || (toffset > value.length - pc)) {            return false;        }        while (--pc >= 0) {            if (ta[to++] != pa[po++]) {                return false;            }        }        return true;    }    /**     */    public boolean startsWith(String prefix) {        return startsWith(prefix, 0);    }    /**     *    测试此字符串是否以指定的后缀结束。     */    public boolean endsWith(String suffix) {        return startsWith(suffix, value.length - suffix.value.length);    }    /**     */    public int hashCode() {        int h = hash;        if (h == 0 && value.length > 0) {            char val[] = value;            for (int i = 0; i < value.length; i++) {                h = 31 * h + val[i];            }            hash = h;        }        return h;    }    /**     *          {@code -1} if the character does not occur.     */    public int indexOf(int ch) {        return indexOf(ch, 0);    }    /**     */    public int indexOf(int ch, int fromIndex) {        final int max = value.length;        if (fromIndex < 0) {            fromIndex = 0;        } else if (fromIndex >= max) {            // Note: fromIndex might be near -1>>>1.            return -1;        }        if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {            // handle most cases here (ch is a BMP code point or a            // negative value (invalid code point))            final char[] value = this.value;            for (int i = fromIndex; i < max; i++) {                if (value[i] == ch) {                    return i;                }            }            return -1;        } else {            return indexOfSupplementary(ch, fromIndex);        }    }    /**     * Handles (rare) calls of indexOf with a supplementary character.     */    private int indexOfSupplementary(int ch, int fromIndex) {        if (Character.isValidCodePoint(ch)) {            final char[] value = this.value;            final char hi = Character.highSurrogate(ch);            final char lo = Character.lowSurrogate(ch);            final int max = value.length - 1;            for (int i = fromIndex; i < max; i++) {                if (value[i] == hi && value[i + 1] == lo) {                    return i;                }            }        }        return -1;    }    /**     */    public int lastIndexOf(int ch) {        return lastIndexOf(ch, value.length - 1);    }    /**     */    public int lastIndexOf(int ch, int 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))            final char[] value = this.value;            int i = Math.min(fromIndex, value.length - 1);            for (; i >= 0; i--) {                if (value[i] == ch) {                    return i;                }            }            return -1;        } else {            return lastIndexOfSupplementary(ch, fromIndex);        }    }    /**     * Handles (rare) calls of lastIndexOf with a supplementary character.     */    private int lastIndexOfSupplementary(int ch, int fromIndex) {        if (Character.isValidCodePoint(ch)) {            final char[] value = this.value;            char hi = Character.highSurrogate(ch);            char lo = Character.lowSurrogate(ch);            int i = Math.min(fromIndex, value.length - 2);            for (; i >= 0; i--) {                if (value[i] == hi && value[i + 1] == lo) {                    return i;                }            }        }        return -1;    }    /**     */    public int indexOf(String str) {        return indexOf(str, 0);    }    /**     */    public int indexOf(String str, int fromIndex) {        return indexOf(value, 0, value.length,                str.value, 0, str.value.length, fromIndex);    }    /**     */    static int indexOf(char[] source, int sourceOffset, int sourceCount,            String target, int fromIndex) {        return indexOf(source, sourceOffset, sourceCount,                       target.value, 0, target.value.length,                       fromIndex);    }    /**     */    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;    }    /**     */    public int lastIndexOf(String str) {        return lastIndexOf(str, value.length);    }    /**     */    public int lastIndexOf(String str, int fromIndex) {        return lastIndexOf(value, 0, value.length,                str.value, 0, str.value.length, fromIndex);    }    /**     */    static int lastIndexOf(char[] source, int sourceOffset, int sourceCount,            String target, int fromIndex) {        return lastIndexOf(source, sourceOffset, sourceCount,                       target.value, 0, target.value.length,                       fromIndex);    }    /**     */    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;        }    }    /**     */    public String substring(int beginIndex) {        if (beginIndex < 0) {            throw new StringIndexOutOfBoundsException(beginIndex);        }        int subLen = value.length - beginIndex;        if (subLen < 0) {            throw new StringIndexOutOfBoundsException(subLen);        }        return (beginIndex == 0) ? this : new String(value, beginIndex, subLen);    }    /**     */    public String substring(int beginIndex, int endIndex) {        if (beginIndex < 0) {            throw new StringIndexOutOfBoundsException(beginIndex);        }        if (endIndex > value.length) {            throw new StringIndexOutOfBoundsException(endIndex);        }        int subLen = endIndex - beginIndex;        if (subLen < 0) {            throw new StringIndexOutOfBoundsException(subLen);        }        return ((beginIndex == 0) && (endIndex == value.length)) ? this                : new String(value, beginIndex, subLen);    }    /**     */    public CharSequence subSequence(int beginIndex, int endIndex) {        return this.substring(beginIndex, endIndex);    }    /**     */    public String concat(String str) {        int otherLen = str.length();        if (otherLen == 0) {            return this;        }        int len = value.length;        char buf[] = Arrays.copyOf(value, len + otherLen);        str.getChars(buf, len);        return new String(buf, true);    }    /**     */    public String replace(char oldChar, char newChar) {        if (oldChar != newChar) {            int len = value.length;            int i = -1;            char[] val = value; /* avoid getfield opcode */            while (++i < len) {                if (val[i] == oldChar) {                    break;                }            }            if (i < len) {                char buf[] = new char[len];                for (int j = 0; j < i; j++) {                    buf[j] = val[j];                }                while (i < len) {                    char c = val[i];                    buf[i] = (c == oldChar) ? newChar : c;                    i++;                }                return new String(buf, true);            }        }        return this;    }    /**     */    public boolean matches(String regex) {        return Pattern.matches(regex, this);    }    /**     */    public boolean contains(CharSequence s) {        return indexOf(s.toString()) > -1;    }    /**     */    public String replaceFirst(String regex, String replacement) {        return Pattern.compile(regex).matcher(this).replaceFirst(replacement);    }    /**     */    public String replaceAll(String regex, String replacement) {        return Pattern.compile(regex).matcher(this).replaceAll(replacement);    }    /**     */    public String replace(CharSequence target, CharSequence replacement) {        return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(                this).replaceAll(Matcher.quoteReplacement(replacement.toString()));    }    /**     */    public String[] split(String regex, int limit) {        /* fastpath if the regex is a         (1)one-char String and this character is not one of the            RegEx's meta characters ".$|()[{^?*+\\", or         (2)two-char String and the first char is the backslash and            the second is not the ascii digit or ascii letter.         */        char ch = 0;        if (((regex.value.length == 1 &&             ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||             (regex.length() == 2 &&              regex.charAt(0) == '\\' &&              (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&              ((ch-'a')|('z'-ch)) < 0 &&              ((ch-'A')|('Z'-ch)) < 0)) &&            (ch < Character.MIN_HIGH_SURROGATE ||             ch > Character.MAX_LOW_SURROGATE))        {            int off = 0;            int next = 0;            boolean limited = limit > 0;            ArrayList<String> list = new ArrayList<>();            while ((next = indexOf(ch, off)) != -1) {                if (!limited || list.size() < limit - 1) {                    list.add(substring(off, next));                    off = next + 1;                } else {    // last one                    //assert (list.size() == limit - 1);                    list.add(substring(off, value.length));                    off = value.length;                    break;                }            }            // If no match was found, return this            if (off == 0)                return new String[]{this};            // Add remaining segment            if (!limited || list.size() < limit)                list.add(substring(off, value.length));            // Construct result            int resultSize = list.size();            if (limit == 0) {                while (resultSize > 0 && list.get(resultSize - 1).length() == 0) {                    resultSize--;                }            }            String[] result = new String[resultSize];            return list.subList(0, resultSize).toArray(result);        }        return Pattern.compile(regex).split(this, limit);    }    /**     */    public String[] split(String regex) {        return split(regex, 0);    }    /**     */    public static String join(CharSequence delimiter, CharSequence... elements) {        Objects.requireNonNull(delimiter);        Objects.requireNonNull(elements);        // Number of elements not likely worth Arrays.stream overhead.        StringJoiner joiner = new StringJoiner(delimiter);        for (CharSequence cs: elements) {            joiner.add(cs);        }        return joiner.toString();    }    /**     */    public static String join(CharSequence delimiter,            Iterable<? extends CharSequence> elements) {        Objects.requireNonNull(delimiter);        Objects.requireNonNull(elements);        StringJoiner joiner = new StringJoiner(delimiter);        for (CharSequence cs: elements) {            joiner.add(cs);        }        return joiner.toString();    }    /**     */    public String toLowerCase(Locale locale) {        if (locale == null) {            throw new NullPointerException();        }        int firstUpper;        final int len = value.length;        /* Now check if there are any characters that need to be changed. */        scan: {            for (firstUpper = 0 ; firstUpper < len; ) {                char c = value[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[len];        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, 0, 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 < len; i += srcCount) {            srcChar = (int)value[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                srcChar == '\u0130') { // LATIN CAPITAL LETTER I WITH DOT ABOVE                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(result, 0, len + resultOffset);    }    /**     */    public String toLowerCase() {        return toLowerCase(Locale.getDefault());    }    /**     */    public String toUpperCase(Locale locale) {        if (locale == null) {            throw new NullPointerException();        }        int firstLower;        final int len = value.length;        /* Now check if there are any characters that need to be changed. */        scan: {            for (firstLower = 0 ; firstLower < len; ) {                int c = (int)value[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;        }        /* result may grow, so i+resultOffset is the write location in result */        int resultOffset = 0;        char[] result = new char[len]; /* may grow */        /* Just copy the first few upperCase characters. */        System.arraycopy(value, 0, 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 < len; i += srcCount) {            srcChar = (int)value[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(result, 0, len + resultOffset);    }    /**     */    public String toUpperCase() {        return toUpperCase(Locale.getDefault());    }    /**     */    public String trim() {        int len = value.length;        int st = 0;        char[] val = value;    /* avoid getfield opcode */        while ((st < len) && (val[st] <= ' ')) {            st++;        }        while ((st < len) && (val[len - 1] <= ' ')) {            len--;        }        return ((st > 0) || (len < value.length)) ? substring(st, len) : this;    }    /**     */    public String toString() {        return this;    }    /**     */    public char[] toCharArray() {        // Cannot use Arrays.copyOf because of class initialization order issues        char result[] = new char[value.length];        System.arraycopy(value, 0, result, 0, value.length);        return result;    }    /**     */    public static String format(String format, Object... args) {        return new Formatter().format(format, args).toString();    }    /**     */    public static String format(Locale l, String format, Object... args) {        return new Formatter(l).format(format, args).toString();    }    /**     */    public static String valueOf(Object obj) {        return (obj == null) ? "null" : obj.toString();    }    /**     */    public static String valueOf(char data[]) {        return new String(data);    }    /**     */    public static String valueOf(char data[], int offset, int count) {        return new String(data, offset, count);    }    /**     */    public static String copyValueOf(char data[], int offset, int count) {        return new String(data, offset, count);    }    /**     */    public static String copyValueOf(char data[]) {        return new String(data);    }    /**     */    public static String valueOf(boolean b) {        return b ? "true" : "false";    }    /**     */    public static String valueOf(char c) {        char data[] = {c};        return new String(data, true);    }    /**     */    public static String valueOf(int i) {        return Integer.toString(i);    }    /**     */    public static String valueOf(long l) {        return Long.toString(l);    }    /**     */    public static String valueOf(float f) {        return Float.toString(f);    }    /**     */    public static String valueOf(double d) {        return Double.toString(d);    }    /**     */    public native String intern();}