/*
 * @(#)String.java	1.130 01/02/09
 *
 * Copyright 1994-2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package java.lang;

import java.util.Hashtable;
import java.util.Locale;
import java.util.Comparator;
import sun.io.ByteToCharConverter;
import sun.io.CharToByteConverter;
import java.io.CharConversionException;
import java.io.UnsupportedEncodingException;
import java.io.ObjectStreamClass;
import java.io.ObjectStreamField;
import java.lang.ref.SoftReference;

/**
 * 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. 
 * <p>
 * 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:
 * <p><blockquote><pre>
 *     String str = "abc";
 * </pre></blockquote><p>
 * is equivalent to:
 * <p><blockquote><pre>
 *     char data[] = {'a', 'b', 'c'};
 *     String str = new String(data);
 * </pre></blockquote><p>
 * Here are some more examples of how strings can be used:
 * <p><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>
 * <p>
 * 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. 
 * <p>
 * The Java language provides special support for the string 
 * concatentation operator ( + ), and for conversion of 
 * other objects to strings. String concatenation is implemented 
 * through the <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, 
 * <i>The Java Language Specification</i>. 
 *
 * @author  Lee Boynton
 * @author  Arthur van Hoff
 * @version 1.130, 02/09/01
 * @see     java.lang.Object#toString()
 * @see     java.lang.StringBuffer
 * @see     java.lang.StringBuffer#append(boolean)
 * @see     java.lang.StringBuffer#append(char)
 * @see     java.lang.StringBuffer#append(char[])
 * @see     java.lang.StringBuffer#append(char[], int, int)
 * @see     java.lang.StringBuffer#append(double)
 * @see     java.lang.StringBuffer#append(float)
 * @see     java.lang.StringBuffer#append(int)
 * @see     java.lang.StringBuffer#append(long)
 * @see     java.lang.StringBuffer#append(java.lang.Object)
 * @see     java.lang.StringBuffer#append(java.lang.String)
 * @see     <a href="package-summary.html#charenc">Character encodings</a>
 * @since   JDK1.0
 */
public final
class String implements java.io.Serializable, Comparable {
    /** The value is used for character storage. */
    private char value[];

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

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

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

    /** The cached converter for each thread. 
     *  Note: These are declared null to minimize the classes
     *  that String must depend on during initialization
     */
    private static ThreadLocal btcConverter = null;
    private static ThreadLocal ctbConverter = null;

    /**
     * Returns a <code>ByteToCharConverter</code> that uses the specified
     * encoding. For efficiency a cache is maintained that holds the last
     * used converter.
     *
     * @param  enc The name of a character encoding
     * @return     ByteToCharConverter for the specified encoding.
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     * @since      1.2
     */
    private static ByteToCharConverter getBTCConverter(String encoding)
                                  throws UnsupportedEncodingException {
        ByteToCharConverter btc = null;
        if (btcConverter == null)
            btcConverter = new ThreadLocal();
        SoftReference ref = (SoftReference)(btcConverter.get());
        if (ref==null || (btc = (ByteToCharConverter)ref.get())==null ||
                          !encoding.equals(btc.getCharacterEncoding())) {
            btc = ByteToCharConverter.getConverter(encoding);
            btcConverter.set(new SoftReference(btc));
        } else {
            btc.reset();
        }
        return btc;
    }

    /**
     * Returns a <code>CharToByteConverter</code> that uses the specified
     * encoding. For efficiency a cache is maintained that holds the last
     * used converter.
     *
     * @param  enc The name of a character encoding
     * @return     CharToByteConverter for the specified encoding.
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     * @since      1.2
     */
    private static CharToByteConverter getCTBConverter(String encoding)
                                  throws UnsupportedEncodingException {
        CharToByteConverter ctb = null;
        if (ctbConverter == null)
            ctbConverter = new ThreadLocal();
        SoftReference ref = (SoftReference)(ctbConverter.get());
        if (ref==null || (ctb = (CharToByteConverter)ref.get())==null ||
                          !encoding.equals(ctb.getCharacterEncoding())) {
            ctb = CharToByteConverter.getConverter(encoding);
            ctbConverter.set(new SoftReference(ctb));
        } else {
            ctb.reset();
        }
        return ctb;
    }

    /** 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 intially 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</code> object so that it 
     * represents an empty character sequence. 
     */
    public String() {
	value = new char[0];
    }

    /**
     * Initializes a newly created <code>String</code> 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. 
     *
     * @param   value   a <code>String</code>.
     */
    public String(String original) {
 	this.count = original.count;
 	if (original.value.length > this.count) {
 	    // 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.
 	    this.value = new char[this.count];
 	    System.arraycopy(original.value, original.offset, 
 			     this.value, 0, this.count);
 	} else {
 	    // The array representing the String is the same
 	    // size as the String, so no point in making a copy.
 	    this.value = original.value;
 	}
    }

    /**
     * Allocates a new <code>String</code> 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.
     * @throws NullPointerException if <code>value</code> is <code>null</code>.
     */
    public String(char value[]) {
	this.count = value.length;
	this.value = (char[])value.clone();
    }

    /**
     * Allocates a new <code>String</code> that contains characters from 
     * a subarray of the character array argument. The <code>offset</code> 
     * argument is the index of the first character of the subarray and 
     * 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      value    array that is the source of characters.
     * @param      offset   the initial offset.
     * @param      count    the length.
     * @exception  IndexOutOfBoundsException  if the <code>offset</code>
     *               and <code>count</code> arguments index characters outside
     *               the bounds of the <code>value</code> array.
     * @exception NullPointerException if <code>value</code> is 
     *               <code>null</code>.
     */
    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 = new char[count];
	this.count = count;
	System.arraycopy(value, offset, this.value, 0, count);
    }

    /**
     * Allocates a new <code>String</code> constructed from a subarray 
     * of an array of 8-bit integer values. 
     * <p>
     * The <code>offset</code> argument is the index of the first byte 
     * of the subarray, and the <code>count</code> argument specifies the 
     * length of the subarray. 
     * <p>
     * Each <code>byte</code> in the subarray is converted to a 
     * <code>char</code> 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</code> constructors that take a character-encoding name or
     * that use the platform's default encoding.
     *
     * @param      ascii     the bytes to be converted to characters.
     * @param      hibyte    the top 8 bits of each 16-bit Unicode character.
     * @param      offset    the initial offset.
     * @param      count     the length.
     * @exception  IndexOutOfBoundsException  if the <code>offset</code>
     *               or <code>count</code> argument is invalid.
     * @exception NullPointerException if <code>ascii</code> is 
     *                       <code>null</code>.
     * @see        java.lang.String#String(byte[], int)
     * @see        java.lang.String#String(byte[], int, int, java.lang.String)
     * @see        java.lang.String#String(byte[], int, int)
     * @see        java.lang.String#String(byte[], java.lang.String)
     * @see        java.lang.String#String(byte[])
     */
    public String(byte ascii[], int hibyte, 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 > ascii.length - count) {
	    throw new StringIndexOutOfBoundsException(offset + count);
	}

	char value[] = new char[count];
	this.count = count;
	this.value = value;

	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));
	    }
	}
    }

    /**
     * Allocates a new <code>String</code> containing characters 
     * constructed from an array of 8-bit integer values. Each character 
     * <i>c</i>in the resulting string is constructed from the 
     * corresponding component <i>b</i> in the byte array such that:
     * <p><blockquote><pre>
     *     <b><i>c</i></b> == (char)(((hibyte & 0xff) << 8)
     *                         | (<b><i>b</i></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</code> constructors that take a character-encoding name or
     * that use the platform's default encoding.
     *
     * @param      ascii    the bytes to be converted to characters.
     * @param      hibyte   the top 8 bits of each 16-bit Unicode character.
     * @exception NullPointerException If <code>ascii</code> is 
     *                      <code>null</code>.
     * @see        java.lang.String#String(byte[], int, int, java.lang.String)
     * @see        java.lang.String#String(byte[], int, int)
     * @see        java.lang.String#String(byte[], java.lang.String)
     * @see        java.lang.String#String(byte[])
     */
    public String(byte ascii[], int hibyte) {
	this(ascii, hibyte, 0, ascii.length);
    }

   /**
     * Construct a new <code>String</code> by converting the specified
     * subarray of bytes using the specified character-encoding converter.  The
     * length of the new <code>String</code> is a function of the encoding, and
     * hence may not be equal to the length of the subarray.
     *
     * @param  bytes   The bytes to be converted into characters
     * @param  offset  Index of the first byte to convert
     * @param  length  Number of bytes to convert
     * @param  btc     A ByteToCharConverter
     * @exception  IndexOutOfBoundsException  if the <code>offset</code>
     *               and <code>count</code> arguments index characters outside
     *               the bounds of the <code>value</code> array.
     */
    private String(byte bytes[], int offset, int length,
		   ByteToCharConverter btc)
    {
        if (length < 0)
            throw new StringIndexOutOfBoundsException("length must be >= 0");
        if (offset < 0)
            throw new StringIndexOutOfBoundsException("offset must be >= 0");
        if (offset > bytes.length-length)
            throw new StringIndexOutOfBoundsException(offset + count);

	int estCount = btc.getMaxCharsPerByte() * length;
	value = new char[estCount];

        try {
	    count = btc.convert(bytes, offset, offset+length,
				value, 0, estCount);
	    count += btc.flush(value, btc.nextCharIndex(), estCount);
	} catch (CharConversionException x) {
	    count = btc.nextCharIndex();
	}

	if (count < estCount) {
	    // A multi-byte format was used:  Trim the char array.
	    char[] trimValue = new char[count];
	    System.arraycopy(value, 0, trimValue, 0, count);
	    value = trimValue;
	}
    }


    /**
     * Construct a new <code>String</code> by converting the specified
     * subarray of bytes using the specified character encoding.  The length of
     * the new <code>String</code> is a function of the encoding, and hence may
     * not be equal to the length of the subarray.
     *
     * @param  bytes   The bytes to be converted into characters
     * @param  offset  Index of the first byte to convert
     * @param  length  Number of bytes to convert
     * @param  enc     The name of a supported
     *                 <a href="package-summary.html#charenc">character
     *                 encoding</a>
     * @throws  UnsupportedEncodingException
     *          if the named encoding is not supported
     * @throws  IndexOutOfBoundsException
     *          if the <code>offset</code> and <code>count</code> arguments
     *          index characters outside the bounds of the <code>value</code>
     *          array.
     * @since JDK1.1
     */
    public String(byte bytes[], int offset, int length, String enc)
	throws UnsupportedEncodingException
    {
	this(bytes, offset, length, getBTCConverter(enc));
    }

    /**
     * Construct a new <code>String</code> by converting the specified array
     * of bytes using the specified character encoding.  The length of the new
     * <code>String</code> is a function of the encoding, and hence may not be
     * equal to the length of the byte array.
     *
     * @param  bytes   The bytes to be converted into characters
     * @param  enc     The name of a supported
     *                 <a href="package-summary.html#charenc">character
     *                 encoding</a>
     *
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     * @since      JDK1.1
     */
    public String(byte bytes[], String enc)
	throws UnsupportedEncodingException
    {
	this(bytes, 0, bytes.length, enc);
    }

    /**
     * Construct a new <code>String</code> by converting the specified
     * subarray of bytes using the platform's default character encoding.  The
     * length of the new <code>String</code> is a function of the encoding, and
     * hence may not be equal to the length of the subarray.
     *
     * @param  bytes   The bytes to be converted into characters
     * @param  offset  Index of the first byte to convert
     * @param  length  Number of bytes to convert
     * @since  JDK1.1
     */
    public String(byte bytes[], int offset, int length) {
	this(bytes, offset, length, ByteToCharConverter.getDefault());
    }

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

    /**
     * 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</code>.
     * @throws NullPointerException If <code>buffer</code> is 
     * <code>null</code>.
     */
    public String (StringBuffer buffer) { 
	synchronized(buffer) { 
	    buffer.setShared();
	    this.value = buffer.getValue();
	    this.offset = 0;
	    this.count = buffer.length();
	}
    }
    
    // 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 16-bit
     * Unicode characters in the string.
     *
     * @return  the length of the sequence of characters represented by this
     *          object.
     */
    public int length() {
	return count;
    }

    /**
     * Returns the character at the specified index. An index ranges
     * from <code>0</code> to <code>length() - 1</code>. The first character 
     * of the sequence is at index <code>0</code>, the next at index 
     * <code>1</code>, and so on, as for array indexing.
     *
     * @param      index   the index of the character.
     * @return     the character at the specified index of this string.
     *             The first character 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];
    }

    /**
     * Copies characters from this string into the destination character 
     * array. 
     * <p>
     * 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: 
     * <p><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>
     * @exception NullPointerException if <code>dst</code> is <code>null</code>
     */
    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.
     * <p>
     * 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>. 
     * The total number of characters to be copied is 
     * <code>srcEnd-srcBegin</code>. The characters, converted to bytes, 
     * are copied into the subarray of <code>dst</code> starting at index 
     * <code>dstBegin</code> and ending at index: 
     * <p><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
     * <code>getBytes(String enc)</code> method, which takes a
     * character-encoding name, or the <code>getBytes()</code> method, which
     * uses the platform's default encoding.
     *
     * @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> 
     * @exception NullPointerException if <code>dst</code> is <code>null</code>
     */
    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++];
 	}
    }

    /**
     * Apply the specified character-encoding converter to this String,
     * storing the resulting bytes into a new byte array.
     *
     * @param  ctb  A CharToByteConverter
     * @return      The resultant byte array
     */
    private byte[] getBytes(CharToByteConverter ctb) {
	ctb.reset();
	int estLength = ctb.getMaxBytesPerChar() * count;
	byte[] result = new byte[estLength];
	int length = 0;
	try { 
	    length += ctb.convertAny(value, offset, (offset + count),
				     result, 0, estLength);
	    length += ctb.flushAny(result, ctb.nextByteIndex(), estLength);
	} catch (CharConversionException e) {
	    throw new InternalError("Converter malfunction: " +
				    ctb.getClass().getName());
	}


	if (length < estLength) {
	    // A short format was used:  Trim the byte array.
	    byte[] trimResult = new byte[length];
	    System.arraycopy(result, 0, trimResult, 0, length);
	    return trimResult;
	}
	else {
	    return result;
	}
    }

    /**
     * Convert this <code>String</code> into bytes according to the specified
     * character encoding, storing the result into a new byte array.
     *
     * @param  enc     The name of a supported
     *                 <a href="package-summary.html#charenc">character
     *                 encoding</a>
     * @return      The resultant byte array
     *
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     * @since      JDK1.1
     */
    public byte[] getBytes(String enc)
	throws UnsupportedEncodingException
    {
	return getBytes(getCTBConverter(enc));
    }

    /**
     * Convert this <code>String</code> into bytes according to the platform's
     * default character encoding, storing the result into a new byte array.
     *
     * @return  the resultant byte array.
     * @since   JDK1.1
     */
    public byte[] getBytes() {
	return getBytes(CharToByteConverter.getDefault());
    }

    /**
     * Compares this string to the specified object.
     * The result is <code>true</code> if and only if the argument is not 
     * <code>null</code> and is a <code>String</code> object that represents 
     * the same sequence of characters as this object. 
     *
     * @param   anObject   the object to compare this <code>String</code>
     *                     against.
     * @return  <code>true</code> if the <code>String </code>are equal;
     *          <code>false</code> otherwise.
     * @see     java.lang.String#compareTo(java.lang.String)
     * @see     java.lang.String#equalsIgnoreCase(java.lang.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 <code>String</code> to another <code>String</code>,
     * 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.
     * <p>
     * Two characters <code>c1</code> and <code>c2</code> 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>==</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</code> to compare this
     *                          <code>String</code> against.
     * @return  <code>true</code> if the argument is not <code>null</code> 
     *          and the <code>String</code>s are equal,
     *          ignoring case; <code>false</code> otherwise.
     * @see     #equals(Object)
     * @see     java.lang.Character#toLowerCase(char)
     * @see java.lang.Character#toUpperCase(char)
     */
    public boolean equalsIgnoreCase(String anotherString) {
	return (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>. 
     * <p>
     * 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 <i>k</i> be the smallest such index; then the string
     * whose character at position <i>k</i> 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.
     * @exception java.lang.NullPointerException if <code>anotherString</code> 
     *          is <code>null</code>.
     */
    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;
    }

    /**
     * Compares this String to another Object.  If the Object is a String,
     * this function behaves like <code>compareTo(String)</code>.  Otherwise,
     * it throws a <code>ClassCastException</code> (as Strings are comparable
     * only to other Strings).
     *
     * @param   o the <code>Object</code> to be compared.
     * @return  the value <code>0</code> if the argument is a string
     *		lexicographically equal to this string; a value less than
     *		<code>0</code> if the argument is a string lexicographically 
     *		greater than this string; and a value greater than
     *		<code>0</code> if the argument is a string lexicographically
     *		less than this string.
     * @exception <code>ClassCastException</code> if the argument is not a
     *		  <code>String</code>. 
     * @see     java.lang.Comparable
     * @since   1.2
     */
    public int compareTo(Object o) {
	return compareTo((String)o);
    }

    /**
     * Returns a Comparator that orders <code>String</code> objects as by
     * <code>compareToIgnoreCase</code>.  This comparator is serializable.
     * <p>
     * Note that this Comparator does <em>not</em> take locale into account,
     * and will result in an unsatisfactory ordering for certain locales.
     * The java.text package provides <em>Collators</em> to allow
     * locale-sensitive ordering.
     *
     * @return  Comparator for case insensitive comparison of strings
     * @see     java.text.Collator#compare(String, String)
     * @since   1.2
     */
    public static final Comparator CASE_INSENSITIVE_ORDER
                                         = new CaseInsensitiveComparator();
    private static class CaseInsensitiveComparator
                         implements Comparator, java.io.Serializable {
	// use serialVersionUID from JDK 1.2.2 for interoperability
	private static final long serialVersionUID = 8575799808933029326L;

        public int compare(Object o1, Object o2) {
            String s1 = (String) o1;
            String s2 = (String) o2;
            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 considerations.
     * This method returns an integer whose sign is that of
     * <code>this.toUpperCase().toLowerCase().compareTo(
     * str.toUpperCase().toLowerCase())</code>.
     * <p>
     * Note that this method does <em>not</em> take locale into account,
     * and will result in an unsatisfactory ordering for certain locales.
     * The java.text package provides <em>collators</em> 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
     *		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. 
     * <p>
     * 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 <i>k</i> less than <tt>len</tt> 
     * such that: 
     * <tt>this.charAt(toffset+<i>k</i>) != other.charAt(ooffset+<i>k</i>)</tt> 
     * </u>
     *
     * @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.
     * @exception java.lang.NullPointerException if <tt>other</tt> is 
     *          <tt>null</tt>.
     */
    public boolean regionMatches(int toffset, String other, int ooffset, 
				 int len) {
	char ta[] = value;
	int to = offset + toffset;
	int tlim = offset + count;
	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. 
     * <p>
     * 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>There is some nonnegative integer <i>k</i> 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 <i>k</i> 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;
	int tlim = offset + count;
	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 this string starts with the specified prefix beginning 
     * a specified index.
     *
     * @param   prefix    the prefix.
     * @param   toffset   where to begin looking in the 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>
     * @exception java.lang.NullPointerException if <code>prefix</code> is 
     *          <code>null</code>.
     */
    public boolean startsWith(String prefix, int toffset) {
	char ta[] = value;
	int to = offset + toffset;
	int tlim = offset + count;
	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.
     * @exception java.lang.NullPointerException if <code>prefix</code> is 
     *          <code>null</code>.
     * @since   JDK1. 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.
     * @exception java.lang.NullPointerException if <code>suffix</code> is 
     *          <code>null</code>.
     */
    public boolean endsWith(String suffix) {
	return startsWith(suffix, count - suffix.count);
    }

    /**
     * Returns a hashcode for this string. The hashcode 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 
     * <i>i</i>th 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 of the first such occurrence is returned -- 
     * that is, the smallest value <i>k</i> such that: 
     * <blockquote><pre>
     * this.charAt(<i>k</i>) == ch
     * </pre></blockquote>
     * is <code>true</code>. If no such character occurs in this string, 
     * then <code>-1</code> is returned.
     *
     * @param   ch   a character.
     * @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.
     * <p>
     * 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--that is, the smallest value <i>k</i> 
     * such that: 
     * <blockquote><pre>
     * (this.charAt(<i>k</i>) == ch) && (<i>k</i> >= fromIndex)
     * </pre></blockquote>
     * is true. If no such character occurs in this string at or after 
     * position <code>fromIndex</code>, then <code>-1</code> is returned.
     * <p>
     * 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.
     *
     * @param   ch          a character.
     * @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;
	}
	for (int i = offset + fromIndex ; i < max ; i++) {
	    if (v[i] == ch) {
		return i - offset;
	    }
	}
	return -1;
    }

    /**
     * Returns the index within this string of the last occurrence of the
     * specified character. That is, the index returned is the largest 
     * value <i>k</i> such that:
     * <blockquote><pre>
     * this.charAt(<i>k</i>) == ch
     * </pre></blockquote>
     * is true. 
     * The String is searched backwards starting at the last character. 
     *
     * @param   ch   a character.
     * @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. That is, the index returned is the largest value <i>k</i> 
     * such that:
     * <blockquote><pre>
     * this.charAt(k) == ch) && (k <= fromIndex)
     * </pre></blockquote>
     * is true.
     *
     * @param   ch          a character.
     * @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;
	
	for (int i = offset + ((fromIndex >= count) ? count - 1 : fromIndex) ; i >= min ; i--) {
	    if (v[i] == ch) {
		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 
     * <i>k</i> such that:
     * <blockquote><pre>
     * this.startsWith(str, <i>k</i>)
     * </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.
     * @exception java.lang.NullPointerException if <code>str</code> is 
     *          <code>null</code>.
     */
    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 <i>k</i> such that:
     * <blockquote><pre>
     * this.startsWith(str, <i>k</i>) && (<i>k</i> >= fromIndex)
     * </pre></blockquote>
     * is <code>true</code>.
     * <p>
     * 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.
     *
     * @param   str         the substring to search for.
     * @param   fromIndex   the index to start the search from.
     * @return  If the string argument occurs as a substring within this
     *          object at a starting index no smaller than
     *          <code>fromIndex</code>, then the index of the first character
     *          of the first such substring is returned. If it does not occur
     *          as a substring starting at <code>fromIndex</code> or beyond,
     *          <code>-1</code> is returned.
     * @exception java.lang.NullPointerException if <code>str</code> is 
     *          <code>null</code>
     */
    public int indexOf(String str, int fromIndex) {
    	char v1[] = value;
    	char v2[] = str.value;
    	int max = offset + (count - str.count);
	if (fromIndex >= count) {
	    if (count == 0 && fromIndex == 0 && str.count == 0) {
		/* There is an empty string at index 0 in an empty string. */
		return 0;
	    }
	    /* Note: fromIndex might be near -1>>>1 */
	    return -1;
	}
    	if (fromIndex < 0) {
    	    fromIndex = 0;
    	}
	if (str.count == 0) {
	    return fromIndex;
	}

    	int strOffset = str.offset;
        char first  = v2[strOffset];
        int i = offset + fromIndex;

    startSearchForFirstChar:
        while (true) {

	    /* Look for first character. */
	    while (i <= max && v1[i] != first) {
		i++;
	    }
	    if (i > max) {
		return -1;
	    }

	    /* Found first character, now look at the rest of v2 */
	    int j = i + 1;
	    int end = j + str.count - 1;
	    int k = strOffset + 1;
	    while (j < end) {
		if (v1[j++] != v2[k++]) {
		    i++;
		    /* Look for str's first char again. */
		    continue startSearchForFirstChar;
		}
	    }
	    return i - offset;	/* Found whole string. */
        }
    }

    /**
     * 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 <i>k</i> 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.
     * @exception java.lang.NullPointerException  if <code>str</code> is 
     *          <code>null</code>.
     */
    public int lastIndexOf(String str) {
	return lastIndexOf(str, count);
    }

    /**
     * Returns the index within this string of the last occurrence of
     * the specified substring.
     * The returned index indicates the start of the substring, and it
     * must be equal to or less than <code>fromIndex</code>. That is, 
     * the index returned is the largest value <i>k</i> such that:
     * <blockquote><pre>
     * this.startsWith(str, k) && (k <= fromIndex)
     * </pre></blockquote>
     * 
     * @param   str         the substring to search for.
     * @param   fromIndex   the index to start the search from. There is no 
     *          restriction on the value of fromIndex. 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: this entire string 
     *          may be searched. If it is negative, it has the same effect 
     *          as if it were -1: -1 is returned.
     * @return  If the string argument occurs one or more times as a substring
     *          within this object at a starting index no greater than
     *          <code>fromIndex</code>, then the index of the first character of
     *          the last such substring is returned. If it does not occur as a
     *          substring starting at <code>fromIndex</code> or earlier,
     *          <code>-1</code> is returned.
     * @exception java.lang.NullPointerException if <code>str</code> is 
     *          <code>null</code>.
     */
    public int lastIndexOf(String str, int fromIndex) {
        /* 
	 * Check arguments; return immediately where possible. For
	 * consistency, don't check for null str.
	 */
        int rightIndex = count - str.count;
	if (fromIndex < 0) {
	    return -1;
	}
	if (fromIndex > rightIndex) {
	    fromIndex = rightIndex;
	}
	/* Empty string always matches. */
	if (str.count == 0) {
	    return fromIndex;
	}

	char v1[] = value;
	char v2[] = str.value;
	int strLastIndex = str.offset + str.count - 1;
	char strLastChar = v2[strLastIndex];
	int min = offset + str.count - 1;
	int i = min + fromIndex;

    startSearchForLastChar:
	while (true) {

	    /* Look for the last character */
	    while (i >= min && v1[i] != strLastChar) {
		i--;
	    }
	    if (i < min) {
		return -1;
	    }

	    /* Found last character, now look at the rest of v2. */
	    int j = i - 1;
	    int start = j - (str.count - 1);
	    int k = strLastIndex - 1;

	    while (j > start) {
	        if (v1[j--] != v2[k--]) {
		    i--;
		    /* Look for str's last char again. */
		    continue startSearchForLastChar;
		}
	    }

	    return start - offset + 1;    /* Found whole string. */
	}
    }

    /**
     * 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