String.java

/*
 * Copyright (c) 2012, Codename One and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Codename One designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *  
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * 
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * 
 * Please contact Codename One through http://www.codenameone.com/ if you 
 * need additional information or have any questions.
 */

package java.lang;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Comparator;

/**
 * The String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class.
 * Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example:
 * is equivalent to:
 * Here are some more examples of how strings can be used:
 * The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase.
 * 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 StringBuffer class and its append method. String conversions are implemented through the method toString, defined by Object and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele, The Java Language Specification.
 * Since: JDK1.0, CLDC 1.0 See Also:Object.toString(), StringBuffer, StringBuffer.append(boolean), StringBuffer.append(char), StringBuffer.append(char[]), StringBuffer.append(char[], int, int), StringBuffer.append(int), StringBuffer.append(long), StringBuffer.append(java.lang.Object), StringBuffer.append(java.lang.String)
 */
public final class String implements java.lang.CharSequence, Comparable<String> {
    
    public static final Comparator<String> CASE_INSENSITIVE_ORDER = new Comparator<String>() {
        public int compare(String o1, String o2){
            return o1.compareToIgnoreCase(o2);
        }
    };
    
    private static ArrayList<String> str = new ArrayList<String>();
    
    private final char[] value;

    private final int offset;

    private final int count;

    private int hashCode;
    
    // cached native string
    private long nsString;
    private static final char[] ZERO_CHAR = new char[0];
    
    /**
     * Initializes a newly created String object so that it represents an empty character sequence.
     */
    public String(){
        value = ZERO_CHAR;
        offset = 0;
        count = 0;        
    }

    /**
     * Construct a new String by converting the specified array of bytes using the platform's default character encoding. The length of the new String is a function of the encoding, and hence may not be equal to the length of the byte array.
     * bytes - The bytes to be converted into characters
     * JDK1.1
     */
    public String(byte[] bytes){
        this(bytes, 0, bytes.length);
    }

    /**
     * Construct a new String by converting the specified subarray of bytes using the platform's default character encoding. The length of the new String is a function of the encoding, and hence may not be equal to the length of the subarray.
     * bytes - The bytes to be converted into charactersoff - Index of the first byte to convertlen - Number of bytes to convert
     * JDK1.1
     */
    public String(byte[] bytes, int off, int len){
        this(bytesToChars(bytes, off, len, "UTF-8"));
    }

    /**
     * Construct a new String by converting the specified subarray of bytes using the specified character encoding. The length of the new String is a function of the encoding, and hence may not be equal to the length of the subarray.
     * bytes - The bytes to be converted into charactersoff - Index of the first byte to convertlen - Number of bytes to convertenc - The name of a character encoding
     * - If the named encoding is not supported
     * JDK1.1
     */
    public String(byte[] bytes, int off, int len, java.lang.String enc) throws java.io.UnsupportedEncodingException{
        this(bytesToChars(bytes, off, len, enc));
    }
    
    public String(byte[] bytes, java.nio.charset.Charset charset) throws java.io.UnsupportedEncodingException {
        this(bytes, 0, bytes.length, charset.displayName());
    }

    /**
     * Construct a new String by converting the specified array of bytes using the specified character encoding. The length of the new String is a function of the encoding, and hence may not be equal to the length of the byte array.
     * bytes - The bytes to be converted into charactersenc - The name of a supported character encoding
     * - If the named encoding is not supported
     * JDK1.1
     */
    public String(byte[] bytes, java.lang.String enc) throws java.io.UnsupportedEncodingException{
        this(bytesToChars(bytes, 0, bytes.length, enc));
    }

    private static native char[] bytesToChars(byte[] b, int off, int len, String encoding); 
    
    /**
     * Allocates a new 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.
     * value - the initial value of the string.
     * - if value is null.
     */
    public String(char[] value){
        this(value, 0, value.length);
    }

    private StringIndexOutOfBoundsException failedBoundsCheck(int arrayLength, int offset, int count) {
        throw new StringIndexOutOfBoundsException(count);
    }

    /**
     * Allocates a new String that contains characters from a subarray of the character array argument. The offset argument is the index of the first character of the subarray and the 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.
     * value - array that is the source of characters.offset - the initial offset.count - the length.
     * - if the offset and count arguments index characters outside the bounds of the value array.
     * - if value is null.
     */
    public String(char[] data, int offset, int charCount){
        if ((offset | charCount) < 0 || charCount > data.length - offset) {
            throw failedBoundsCheck(data.length, offset, charCount);
        }
        this.offset = 0;
        this.value = new char[charCount];
        this.count = charCount;
        System.arraycopy(data, offset, value, 0, count);
    }

    String(int offset, int charCount, char[] data) {
        if ((offset | charCount) < 0 || charCount > data.length - offset) {
            throw failedBoundsCheck(data.length, offset, charCount);
        }
        this.offset = offset;
        this.value = data;
        this.count = charCount;
    }
    
    /**
     * Initializes a newly created 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.
     * value - a String.
     */
    public String(java.lang.String value){
        this.offset = value.offset;
        this.value = value.value;
        this.count = value.count;
    }

    /**
     * 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.
     * buffer - a StringBuffer.
     * - If buffer is null.
     */
    public String(java.lang.StringBuffer buffer){
        this.offset = 0;
        this.count = buffer.length();
        this.value = new char[count];
        buffer.getChars(0, count, value, 0);
    }
    
    public String(java.lang.StringBuilder buffer) {
        this.offset = 0;
        this.count = buffer.length();
        this.value = new char[count];
        buffer.getChars(0, count, value, 0);
    }

    /**
     * Returns the character at the specified index. An index ranges from 0 to length() - 1. The first character of the sequence is at index 0, the next at index 1, and so on, as for array indexing.
     */
    public final native char charAt(int index);//{
//        return value[offset + index];
//    }

    /**
     * Compares two strings lexicographically. The comparison is based on the Unicode value of each character in the strings. The character sequence represented by this String object is compared lexicographically to the character sequence represented by the argument string. The result is a negative integer if this String object lexicographically precedes the argument string. The result is a positive integer if this String object lexicographically follows the argument string. The result is zero if the strings are equal; compareTo returns 0 exactly when the
     * method would return true.
     * This is the definition of lexicographic ordering. If two strings are different, then either they have different characters at some index that is a valid index for both strings, or their lengths are different, or both. If they have different characters at one or more index positions, let k be the smallest such index; then the string whose character at position k has the smaller value, as determined by using the < operator, lexicographically precedes the other string. In this case, compareTo returns the difference of the two character values at position k in the two string -- that is, the value:
     * this.charAt(k)-anotherString.charAt(k) If there is no index position at which they differ, then the shorter string lexicographically precedes the longer string. In this case, compareTo returns the difference of the lengths of the strings -- that is, the value: this.length()-anotherString.length()
     */
    public int compareTo(java.lang.String anotherString){
        if(anotherString == this) {
            return 0;
        }
        int minL = Math.min(anotherString.length(), length());
        for(int iter = 0 ; iter < minL ; iter++) {
            char a = value[offset + iter];
            char b = anotherString.value[anotherString.offset + iter];
            if(a != b) {
                return a - b;
            }
        }
        return length() - anotherString.length(); 
    }
    
    public int compareToIgnoreCase(java.lang.String anotherString) {
        if (anotherString == this) {
            return 0;
        }
        return toLowerCase().compareTo(anotherString.toLowerCase());
    }
    
    public boolean contentEquals(CharSequence cs) {
        if (cs == null) return false;
        return equals(cs.toString());
    }
    
    public boolean contentEquals(StringBuffer buf) {
        if (null == buf) return false;
        return equals(buf.toString());
    }
    
    public static String copyValueOf(char[] data) {
        return new String(data);
    }
    
    public static String copyValueOf(char[] data, int offset, int count) {
        return new String(data, offset, count);
    }

    /**
     * Concatenates the specified string to the end of this string.
     * If the length of the argument string is 0, then this String object is returned. Otherwise, a new String object is created, representing a character sequence that is the concatenation of the character sequence represented by this String object and the character sequence represented by the argument string.
     * Examples:
     * "cares".concat("s") returns "caress" "to".concat("get").concat("her") returns "together"
     */
    public java.lang.String concat(java.lang.String str){
        char[] n = new char[length() + str.length()];
        System.arraycopy(value, offset, n, 0, count);
        System.arraycopy(str.value, str.offset, n, count, str.count);
        return new String(n); 
    }

    /**
     * Tests if this string ends with the specified suffix.
     */
    public boolean endsWith(java.lang.String suffix){
        if(suffix.length() > length()) {
            return false;
        }
        int offset = suffix.length() - 1;
        for(int iter = length() - 1 ; offset >= 0 ; iter--) {
            if(value[this.offset + iter] != suffix.value[suffix.offset + offset]) {
                return false;
            }
            offset--;
        }
        return true;
    }

    /**
     * Compares this string to the specified object. The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object.
     */
    public native boolean equals(java.lang.Object anObject);
    /*public boolean equals(java.lang.Object anObject){
        if(anObject == this) {
            return true;
        }
        if(anObject == null || anObject.getClass() != getClass()) {
            return false;
        }
        String s = (String)anObject;
        if(s.length() != length()) {
            return false;
        }
        for(int iter = 0 ; iter < count ; iter++) {
            if(value[offset + iter] != s.value[s.offset + iter]) {
                return false;
            }
        }
        return true;
    }*/

    /**
     * Compares this String to another 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 c1 and c2 are considered the same, ignoring case if at least one of the following is true: The two characters are the same (as compared by the == operator). Applying the method Character.toUpperCase(char) to each character produces the same result. Applying the method Character.toLowerCase(char) to each character produces the same result.
     */
    public native boolean equalsIgnoreCase(java.lang.String s);

    /**
     * Convert this String into bytes according to the platform's default character encoding, storing the result into a new byte array.
     */
    public byte[] getBytes(){
        try {
            return getBytes("UTF-8"); 
        } catch(java.io.UnsupportedEncodingException e) {
            // dumbass checked exception
            return null;
        }
    }

    private static native byte[] charsToBytes(char[] arr, char[] encoding);
    
    /**
     * Convert this String into bytes according to the specified character encoding, storing the result into a new byte array.
     */
    public byte[] getBytes(java.lang.String enc) throws java.io.UnsupportedEncodingException{
        if(offset == 0 && value.length == count) {
            if(enc == null) {
                return charsToBytes(toCharNoCopy(), null); 
            }
            return charsToBytes(toCharNoCopy(), enc.toCharNoCopy()); 
        } 
        if(enc == null) {
            return charsToBytes(toCharArray(), null); 
        }
        return charsToBytes(toCharArray(), enc.toCharNoCopy()); 
    }
    
    public byte[] getBytes(Charset charset) throws java.io.UnsupportedEncodingException {
        return getBytes(charset.displayName());
    }

    /**
     * Copies characters from this string into the destination character array.
     * The first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1 (thus the total number of characters to be copied is srcEnd-srcBegin). The characters are copied into the subarray of dst starting at index dstBegin and ending at index:
     * dstbegin + (srcEnd-srcBegin) - 1
     */
    public native void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin);//{
//        for(int iter = srcBegin ; iter < srcEnd ; iter++) {
//            dst[dstBegin] = value[offset + iter];
//            dstBegin++;
//        }
//    }

    /**
     * Returns a hashcode for this string. The hashcode for a String object is computed as s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1] using int arithmetic, where s[i] is the
     * th character of the string, n is the length of the string, and ^ indicates exponentiation. (The hash value of the empty string is zero.)
     */
    public native int hashCode();

    /**
     * Returns the index within this string of the first occurrence of the specified character. If a character with value ch occurs in the character sequence represented by this String object, then the index of the first such occurrence is returned -- that is, the smallest value
     * such that: this.charAt(
     * ) == ch is true. If no such character occurs in this string, then -1 is returned.
     */
    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 ch occurs in the character sequence represented by this String object at an index no smaller than fromIndex, then the index of the first such occurrence is returned--that is, the smallest value k such that:
     * (this.charAt(
     * ) == ch) &amp;&amp; (
     * >= fromIndex) is true. If no such character occurs in this string at or after position fromIndex, then -1 is returned.
     * There is no restriction on the value of fromIndex. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: -1 is returned.
     */
    public native int indexOf(int ch, int fromIndex);//{
//        for(int iter = offset + fromIndex ; iter < count + offset ; iter++) {
//            if(value[iter] == ch) {
//                return iter - offset;
//            }
//        }
//        return -1; 
//    }

    /**
     * Returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value
     * such that: this.startsWith(str,
     * ) is true.
     */
    public int indexOf(java.lang.String string){
        int start = 0;
        int subCount = string.count;
        int _count = count;
        if (subCount > 0) {
            if (subCount > _count) {
                return -1;
            }
            char[] target = string.value;
            int subOffset = string.offset;
            char firstChar = target[subOffset];
            int end = subOffset + subCount;
            while (true) {
                int i = indexOf(firstChar, start);
                if (i == -1 || subCount + i > _count) {
                    return -1; // handles subCount > count || start >= count
                }
                int o1 = offset + i, o2 = subOffset;
                char[] _value = value;
                while (++o2 < end && _value[++o1] == target[o2]) {
                    // Intentionally empty
                }
                if (o2 == end) {
                    return i;
                }
                start = i + 1;
            }
        }
        return start < _count ? start : _count;
    }

    /**
     * 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
     * such that: this.startsWith(str,
     * ) &amp;&amp; (
     * >= fromIndex) is true.
     * There is no restriction on the value of fromIndex. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: -1 is returned.
     */
    public int indexOf(java.lang.String subString, int start){
        if (start < 0) {
            start = 0;
        }
        int subCount = subString.count;
        int _count = count;
        if (subCount > 0) {
            if (subCount + start > _count) {
                return -1;
            }
            char[] target = subString.value;
            int subOffset = subString.offset;
            char firstChar = target[subOffset];
            int end = subOffset + subCount;
            while (true) {
                int i = indexOf(firstChar, start);
                if (i == -1 || subCount + i > _count) {
                    return -1; // handles subCount > count || start >= count
                }
                int o1 = offset + i, o2 = subOffset;
                char[] _value = value;
                while (++o2 < end && _value[++o1] == target[o2]) {
                    // Intentionally empty
                }
                if (o2 == end) {
                    return i;
                }
                start = i + 1;
            }
        }
        return start < _count ? start : _count;
    }

    /**
     * Returns a canonical representation for the string object.
     * A pool of strings, initially empty, is maintained privately by the class String.
     * When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.
     * It follows that for any two strings s and t, s.intern()==t.intern() is true if and only if s.equals(t) is true.
     * All literal strings and string-valued constant expressions are interned. String literals are defined in Section 3.10.5 of the Java Language Specification
     */
    public java.lang.String intern() {
        int off = str.indexOf(this);
        if(off > -1) {
            return str.get(off);
        }
        str.add(this);
        return this;
    }

    /**
     * Returns the index within this string of the last occurrence of the specified character. That is, the index returned is the largest value
     * such that: this.charAt(
     * ) == ch is true. The String is searched backwards starting at the last character.
     */
    public int lastIndexOf(int ch){
        for(int iter = count + offset - 1 ; iter >= offset ; iter--) {
            if(value[iter] == ch) {
                return iter - offset;
            }
        }
        return -1; 
    }

    /**
     * Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. That is, the index returned is the largest value
     * such that: (this.charAt(k) == ch) &amp;&amp; (k  &lt;= fromIndex) is true.
     */
    public int lastIndexOf(int ch, int start){
        int _count = count;
        int _offset = offset;
        char[] _value = value;
        if (start >= 0) {
            if (start >= _count) {
                start = _count - 1;
            }
            for (int i = _offset + start; i >= _offset; --i) {
                if (_value[i] == ch) {
                    return i - _offset;
                }
            }
        }
        return -1;
    }
    
    /**
     * Searches in this string for the last index of the specified string. The
     * search for the string starts at the end and moves towards the beginning
     * of this string.
     * 
     * @param string
     *            the string to find.
     * @return the index of the first character of the specified string in this
     *         string, -1 if the specified string is not a substring.
     * @throws NullPointerException
     *             if {@code string} is {@code null}.
     */
    public int lastIndexOf(String string) {
        return lastIndexOf(string, length());
    }

    /**
     * Searches in this string for the index of the specified string. The search
     * for the string starts at the specified offset and moves towards the
     * beginning of this string.
     * 
     * @param subString
     *            the string to find.
     * @param start
     *            the starting offset.
     * @return the index of the first character of the specified string in this
     *         string , -1 if the specified string is not a substring.
     * @throws NullPointerException
     *             if {@code subString} is {@code null}.
     */
    public int lastIndexOf(String subString, int start) {
        int count = length();
        int subCount = subString.length();
        if (subCount <= count && start >= 0) {
            if (subCount > 0) {
                if (start > count - subCount) {
                    start = count - subCount;
                }
                // count and subCount are both >= 1
                char[] target = subString.toCharArray();
                int subOffset = 0;
                char firstChar = target[subOffset];
                int end = subOffset + subCount;
                while (true) {
                    int i = lastIndexOf(firstChar, start);
                    if (i == -1) {
                        return -1;
                    }
                    int o1 = i, o2 = subOffset;
                    while (++o2 < end && value[offset + (++o1)] == target[o2]) {
                        // Intentionally empty
                    }
                    if (o2 == end) {
                        return i;
                    }
                    start = i - 1;
                }
            }
            return start < count ? start : count;
        }
        return -1;
    }

    
    /**
     * Returns the length of this string. The length is equal to the number of 16-bit Unicode characters in the string.
     */
    public int length(){
        return count;
    }
    
    /**
     * Compares the specified string to this string and compares the specified
     * range of characters to determine if they are the same.
     *
     * @param thisStart
     *            the starting offset in this string.
     * @param string
     *            the string to compare.
     * @param start
     *            the starting offset in the specified string.
     * @param length
     *            the number of characters to compare.
     * @return {@code true} if the ranges of characters are equal, {@code false}
     *         otherwise
     * @throws NullPointerException
     *             if {@code string} is {@code null}.
     */
    public boolean regionMatches(int thisStart, String string, int start, int length) {
        if (string == null) {
            throw new NullPointerException("string == null");
        }
        if (start < 0 || string.count - start < length) {
            return false;
        }
        if (thisStart < 0 || count - thisStart < length) {
            return false;
        }
        if (length <= 0) {
            return true;
        }
        int o1 = offset + thisStart, o2 = string.offset + start;
        char[] value1 = value;
        char[] value2 = string.value;
        for (int i = 0; i < length; ++i) {
            if (value1[o1 + i] != value2[o2 + i]) {
                return false;
            }
        }
        return true;
    }

    /**
     * Tests if two string regions are equal.
     * A substring of this String object is compared to a substring of the argument other. The result is true if these substrings represent character sequences that are the same, ignoring case if and only if ignoreCase is true. The substring of this String object to be compared begins at index toffset and has length len. The substring of other to be compared begins at index ooffset and has length len. The result is false if and only if at least one of the following is true: toffset is negative. ooffset is negative. toffset+len is greater than the length of this String object. ooffset+len is greater than the length of the other argument. There is some nonnegative integer k less than len such that:
     * this.charAt(toffset+k) != other.charAt(ooffset+k) ignoreCase is true and there is some nonnegative integer
     * less than len such that: Character.toLowerCase(this.charAt(toffset+k)) != Character.toLowerCase(other.charAt(ooffset+k)) and: Character.toUpperCase(this.charAt(toffset+k)) != Character.toUpperCase(other.charAt(ooffset+k))
     */
    public boolean regionMatches(boolean ignoreCase, int thisStart, String string, int start, int length) {
        if (!ignoreCase) {
            return regionMatches(thisStart, string, start, length);
        }
        if (string == null) {
            throw new NullPointerException("string == null");
        }
        if (thisStart < 0 || length > count - thisStart) {
            return false;
        }
        if (start < 0 || length > string.count - start) {
            return false;
        }
        thisStart += offset;
        start += string.offset;
        int end = thisStart + length;
        char[] target = string.value;
        while (thisStart < end) {
            char c1 = value[thisStart++];
            char c2 = target[start++];
            if (c1 != c2 && foldCase(c1) != foldCase(c2)) {
                return false;
            }
        }
        return true;
    }
    
    /**
     * This isn't equivalent to either of ICU's u_foldCase case folds, and thus any of the Unicode
     * case folds, but it's what the RI uses.
     */
    private char foldCase(char ch) {
        if (ch < 128) {
            if ('A' <= ch && ch <= 'Z') {
                return (char) (ch + ('a' - 'A'));
            }
            return ch;
        }
        return Character.toLowerCase(Character.toUpperCase(ch));
    }

    /**
     * Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
     * If the character oldChar does not occur in the character sequence represented by this String object, then a reference to this String object is returned. Otherwise, a new String object is created that represents a character sequence identical to the character sequence represented by this String object, except that every occurrence of oldChar is replaced by an occurrence of newChar.
     * Examples:
     * "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)
     */
    public java.lang.String replace(char oldChar, char newChar){
        char[] buffer = value;
        int _offset = offset;
        int _count = count;

        int idx = _offset;
        int last = _offset + _count;
        boolean copied = false;
        while (idx < last) {
            if (buffer[idx] == oldChar) {
                if (!copied) {
                    char[] newBuffer = new char[_count];
                    System.arraycopy(buffer, _offset, newBuffer, 0, _count);
                    buffer = newBuffer;
                    idx -= _offset;
                    last -= _offset;
                    copied = true;
                }
                buffer[idx] = newChar;
            }
            idx++;
        }

        return copied ? new String(buffer) : this;
    }

    /**
     * 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".
     */
    public java.lang.String replace(java.lang.CharSequence target, java.lang.CharSequence replacement) {
        if (target == null) {
            throw new NullPointerException("target");
        }
        if (replacement == null) {
            throw new NullPointerException("replacement");
        }
        java.lang.String targetStr = target.toString();
        java.lang.String replacementStr = replacement.toString();
        int targetLen = targetStr.length();
        if (targetLen == 0) {
            int len = count;
            StringBuilder sb = new StringBuilder(len + (len + 1) * replacementStr.length());
            sb.append(replacementStr);
            for (int i = 0; i < len; i++) {
                sb.append(value[offset + i]);
                sb.append(replacementStr);
            }
            return sb.toString();
        }
        int idx = indexOf(targetStr);
        if (idx < 0) {
            return this;
        }
        StringBuilder sb = new StringBuilder(count);
        int prev = 0;
        while (idx >= 0) {
            sb.append(value, offset + prev, idx - prev);
            sb.append(replacementStr);
            prev = idx + targetLen;
            idx = indexOf(targetStr, prev);
        }
        sb.append(value, offset + prev, count - prev);
        return sb.toString();
    }

    /**
     * Tests if this string starts with the specified prefix.
     */
    public boolean startsWith(java.lang.String prefix){
        return startsWith(prefix, 0);
    }

    /**
     * Tests if this string starts with the specified prefix beginning at the specified index.
     */
    public boolean startsWith(java.lang.String prefix, int toffset){
        if(toffset + prefix.count > count) {
            return false;
        }
        for(int iter = 0 ; iter < prefix.count ; iter++) {
            if(prefix.value[iter+prefix.offset] != value[iter + toffset + offset]) {
                return false;
            }
        }
        return true; 
    }

    /**
     * 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:
     * "unhappy".substring(2) returns "happy" "Harbison".substring(3) returns "bison" "emptiness".substring(9) returns "" (an empty string)
     */
    public java.lang.String substring(int start){
        if (start == 0) {
            return this;
        }
        if (start >= 0 && start <= count) {
            //return new String(offset + start, count - start, value);
            return new String(value, offset + start, count - start);
        }
        throw new ArrayIndexOutOfBoundsException(start);
    }

    /**
     * Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex.
     * Examples:
     * "hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile"
     */
    public java.lang.String substring(int start, int end) {
        if (start == 0 && end == count) {
            return this;
        }
        // NOTE last character not copied!
        // Fast range check.
        if (start >= 0 && start <= end && end <= count) {
            //return new String(offset + start, end - start, value);
            return new String(value, offset + start, end - start);
        }
        throw new ArrayIndexOutOfBoundsException(start);
    }

    private char[] toCharNoCopy() {
        if(offset == 0 && value.length == count) {
            return value;
        }
        return toCharArray();
    }
    
    /**
     * Converts this string to a new character array.
     */
    public char[] toCharArray(){
        char[] buffer = new char[count];
        System.arraycopy(value, offset, buffer, 0, count);
        return buffer;
    }

    /**
     * Converts all of the characters in this String to lower case.
     */
//    public java.lang.String toLowerCase(){
//        char[] c = new char[length()];
//        for(int iter = 0 ; iter < count ; iter++) {
//            c[iter] = Character.toLowerCase(value[offset + iter]);
//        }
//        return new String(c);
//    }
    
    public native java.lang.String toLowerCase();

    /**
     * This object (which is already a string!) is itself returned.
     */
    public native java.lang.String toString();

    /**
     * Converts all of the characters in this String to upper case.
     */
//    public java.lang.String toUpperCase(){
//        char[] c = new char[length()];
//        for(int iter = 0 ; iter < count ; iter++) {
//            c[iter] = Character.toUpperCase(value[offset + iter]);
//        }
//        return new String(c);
//    }

    public native java.lang.String toUpperCase();
    
    public java.lang.String toUpperCase(java.util.Locale locale) {
        return toUpperCase();
    }
    
    /**
     * Removes white space from both ends of this string.
     * If this String object represents an empty character sequence, or the first and last characters of character sequence represented by this String object both have codes greater than 'u0020' (the space character), then a reference to this String object is returned.
     * Otherwise, if there is no character with a code greater than 'u0020' in the string, then a new String 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 'u0020', and let m be the index of the last character in the string whose code is greater than 'u0020'. A new String 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 this.substring(k,m+1).
     * This method may be used to trim whitespace from the beginning and end of a string; in fact, it trims all ASCII control characters as well.
     */
    public java.lang.String trim(){
        int start = offset, last = offset + count - 1;
        int end = last;
        while ((start <= end) && (value[start] <= ' ')) {
            start++;
        }
        while ((end >= start) && (value[end] <= ' ')) {
            end--;
        }
        if (start == offset && end == last) {
            return this;
        }
        //return new String(start, end - start + 1, value);
        return new String(value, start, end - start + 1);
    }

    /**
     * Returns the string representation of the boolean argument.
     */
    public static java.lang.String valueOf(boolean value){
        return value ? "true" : "false";
    }

    /**
     * Returns the string representation of the char argument.
     */
    public static java.lang.String valueOf(char value){
        String s = new String(0, 1, new char[] { value });
        s.hashCode = value;
        return s;
    }

    public static java.lang.String valueOf(char[] data){
        return new String(data, 0, data.length);
    }

    /**
     * Returns the string representation of a specific subarray of the char array argument.
     * The offset argument is the index of the first character of the subarray. The 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.
     */
    public static java.lang.String valueOf(char[] data, int start, int length){
        return new String(data, start, length);
    }

    /**
     * Returns the string representation of the double argument.
     * The representation is exactly the one returned by the Double.toString method of one argument.
     */
    public static java.lang.String valueOf(double value){
        return Double.toString(value);
    }

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

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

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

    /**
     * Returns the string representation of the Object argument.
     */
    public static java.lang.String valueOf(java.lang.Object obj){
        return obj == null ? "null" : obj.toString();
    }

    @Override
    public CharSequence subSequence(int start, int end) {
        return substring(start, end);
    }

    protected void finalize() {
        if(nsString != 0) {
            releaseNSString(nsString);
        }
        nsString = 0;
    }
    
    private native static void releaseNSString(long ns);
    
    
    public native static String format(String format, Object... args);
    
    public boolean contains(CharSequence seq) {
        return seq == null ? false : indexOf(seq.toString()) != -1;
    }
    
    public boolean isEmpty() {
        return length() == 0;
    }
}