/*
 
* Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
 
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
* This code is free software; you can redistribute it and/or modify it
 
* under the terms of the GNU General Public License version 2 only, as
 
* published by the Free Software Foundation.
  
Oracle designates this
 
* particular file as subject to the "Classpath" exception as provided
 
* by Oracle in the LICENSE file that accompanied this code.
 
*
 
* This code is distributed in the hope that it will be useful, but WITHOUT
 
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 
* FITNESS FOR A PARTICULAR PURPOSE.
  
See the GNU General Public License
 
* version 2 for more details (a copy is included in the LICENSE file that
 
* accompanied this code).
 
*
 
* You should have received a copy of the GNU General Public License version
 
* 2 along with this work; if not, write to the Free Software Foundation,
 
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 
*
 
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 
* or visit www.oracle.com if you need additional information or have any
 
* questions.
 
*/

package java.lang;

import sun.misc.FloatingDecimal;
import java.util.Arrays;

/**
 
* A mutable sequence of characters.
 
* <p>
 
* Implements a modifiable string. At any point in time it contains some
 
* particular sequence of characters, but the length and content of the
 
* sequence can be changed through certain method calls.
 
*
 
* <p>Unless otherwise noted, passing a {@code null} argument to a constructor
 
* or method in this class will cause a {@link NullPointerException} to be
 
* thrown.
 
*
 
* @author
      
Michael McCloskey
 
* @author
      
Martin Buchholz
 
* @author
      
Ulf Zibis
 
* @since
       
1.5
 
*/

abstract class AbstractStringBuilder implements Appendable, CharSequence {
    
/**
     
* The value is used for character storage.
     
*/
    
char[] value;

    
/**
     
* The count is the number of characters used.
     
*/
    
int count;

    
/**
     
* This no-arg constructor is necessary for serialization of subclasses.
     
*/

    
AbstractStringBuilder() {
    
}

    
/**
     
* Creates an AbstractStringBuilder of the specified capacity.
     
*/
    
AbstractStringBuilder(int capacity) {
        
value = new char[capacity];
    
}

    
/**
     
* Returns the length (character count).
     
*
     
* @return
  
the length of the sequence of characters currently
     
*
          
represented by this object
     
*/

    
@Override
    
public int length() {
        
return count;
    
}

    
/**
     
* Returns the current capacity. The capacity is the amount of storage
     
* available for newly inserted characters, beyond which an allocation
     
* will occur.
     
*
     
* @return
  
the current capacity
     
*/

    
public int capacity() {
        
return value.length;
    
}

    
/**
     
* Ensures that the capacity is at least equal to the specified minimum.
     
* If the current capacity is less than the argument, then a new internal
     
* array is allocated with greater capacity. The new capacity is the
     
* larger of:
     
* <ul>
     
* <li>The {@code minimumCapacity} argument.
     
* <li>Twice the old capacity, plus {@code 2}.
     
* </ul>
     
* If the {@code minimumCapacity} argument is nonpositive, this
     
* method takes no action and simply returns.
     
* Note that subsequent operations on this object can reduce the
     
* actual capacity below that requested here.
     
*
     
* @param
   
minimumCapacitythe minimum desired capacity.
     
*/

    
public void ensureCapacity(int minimumCapacity) {
        
if (minimumCapacity > 0)
            
ensureCapacityInternal(minimumCapacity);
    
}

    
/**
     
* For positive values of {@code minimumCapacity}, this method
     
* behaves like {@code ensureCapacity}, however it is never
     
* synchronized.
     
* If {@code minimumCapacity} is non positive due to numeric
     
* overflow, this method throws {@code OutOfMemoryError}.
     
*/

    
private void ensureCapacityInternal(int minimumCapacity) {
        
// overflow-conscious code
        
if (minimumCapacity - value.length > 0) {
            
value = Arrays.copyOf(value,
                    
newCapacity(minimumCapacity));
        
}
    
}

    
/**
     
* The maximum size of array to allocate (unless necessary).
     
* Some VMs reserve some header words in an array.
     
* Attempts to allocate larger arrays may result in
     
* OutOfMemoryError: Requested array size exceeds VM limit
     
*/

    
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

    
/**
     
* Returns a capacity at least as large as the given minimum capacity.
     
* Returns the current capacity increased by the same amount + 2 if
     
* that suffices.
     
* Will not return a capacity greater than {@code MAX_ARRAY_SIZE}
     
* unless the given minimum capacity is greater than that.
     
*
     
* @param
  
minCapacity the desired minimum capacity
     
* @throws OutOfMemoryError if minCapacity is less than zero or
     
*
         
greater than Integer.MAX_VALUE
     
*/

    
private int newCapacity(int minCapacity) {
        
// overflow-conscious code
        
int newCapacity = (value.length << 1) + 2;
        
if (newCapacity - minCapacity < 0) {
            
newCapacity = minCapacity;
        
}
        
return (newCapacity <= 0 || MAX_ARRAY_SIZE - newCapacity < 0)
            
? hugeCapacity(minCapacity)
            
: newCapacity;
    
}

    
private int hugeCapacity(int minCapacity) {
        
if (Integer.MAX_VALUE - minCapacity < 0) { // overflow
            
throw new OutOfMemoryError();
        
}
        
return (minCapacity > MAX_ARRAY_SIZE)
            
? minCapacity : MAX_ARRAY_SIZE;
    
}

    
/**
     
* Attempts to reduce storage used for the character sequence.
     
* If the buffer is larger than necessary to hold its current sequence of
     
* characters, then it may be resized to become more space efficient.
     
* Calling this method may, but is not required to, affect the value
     
* returned by a subsequent call to the
 
 
method.
     
*/

    
public void trimToSize() {
        
if (count < value.length) {
            
value = Arrays.copyOf(value, count);
        
}
    
}

    
/**
     
* Sets the length of the character sequence.
     
* The sequence is changed to a new character sequence
     
* whose length is specified by the argument. For every nonnegative
     
* index <i>k</i> less than {@code newLength}, the character at
     
* index <i>k</i> in the new character sequence is the same as the
     
* character at index <i>k</i> in the old sequence if <i>k</i> is less
     
* than the length of the old character sequence; otherwise, it is the
     
* null character {@code '\u005Cu0000'}.
     
*
     
* In other words, if the {@code newLength} argument is less than
     
* the current length, the length is changed to the specified length.
     
* <p>
     
* If the {@code newLength} argument is greater than or equal
     
* to the current length, sufficient null characters
     
* ({@code '\u005Cu0000'}) are appended so that
     
* length becomes the {@code newLength} argument.
     
* <p>
     
* The {@code newLength} argument must be greater than or equal
     
* to {@code 0}.
     
*
     
* @param
      
newLength
   
the new length
     
* @throwsIndexOutOfBoundsException
  
if the
     
*
               
{@code newLength} argument is negative.
     
*/

    
public void setLength(int newLength) {
        
if (newLength < 0)
            
throw new StringIndexOutOfBoundsException(newLength);
        
ensureCapacityInternal(newLength);

        
if (count < newLength) {
            
Arrays.fill(value, count, newLength, '\0');
        
}

        
count = newLength;
    
}

    
/**
     
* Returns the {@code char} value in this sequence at the specified index.
     
* The first {@code char} value is at index {@code 0}, the next at index
     
* {@code 1}, and so on, as in array indexing.
     
* <p>
     
* The index argument must be greater than or equal to
     
* {@code 0}, and less than the length of this sequence.
     
*
     
* <p>If the {@code char} value specified by the index is a
     
*
 
<a href="Character.html#unicode">surrogate</a>, the surrogate
     
* value is returned.
     
*
     
* @param
      
index
   
the index of the desired {@code char} value.
     
* @returnthe {@code char} value at the specified index.
     
* @throwsIndexOutOfBoundsException
  
if {@code index} is
     
*
             
negative or greater than or equal to {@code length()}.
     
*/

    
@Override
    
public char charAt(int index) {
        
if ((index < 0) || (index >= count))
            
throw new StringIndexOutOfBoundsException(index);
        
return value[index];
    
}

    
/**
     
* Returns the character (Unicode code point) at the specified
     
* index. The index refers to {@code char} values
     
* (Unicode code units) and ranges from {@code 0} to
     
*
 
{@code
  
- 1}.
     
*
     
* <p> If the {@code char} value specified at the given index
     
* is in the high-surrogate range, the following index is less
     
* than the length of this sequence, and the
     
* {@code char} value at the following index is in the
     
* low-surrogate range, then the supplementary code point
     
* corresponding to this surrogate pair is returned. Otherwise,
     
* the {@code char} value at the given index is returned.
     
*
     
* @param
      
index the index to the {@code char} values
     
* @returnthe code point value of the character at the
     
*
             
{@code index}
     
* @exception
  
IndexOutOfBoundsExceptionif the {@code index}
     
*
             
argument is negative or not less than the length of this
     
*
             
sequence.
     
*/

    
public int codePointAt(int index) {
        
if ((index < 0) || (index >= count)) {
            
throw new StringIndexOutOfBoundsException(index);
        
}
        
return Character.codePointAtImpl(value, index, count);
    
}

    
/**
     
* Returns the character (Unicode code point) before the specified
     
* index. The index refers to {@code char} values
     
* (Unicode code units) and ranges from {@code 1} to {@link
     
* #length()}.
     
*
     
* <p> If the {@code char} value at {@code (index - 1)}
     
* is in the low-surrogate range, {@code (index - 2)} is not
     
* negative, and the {@code char} value at {@code (index -
     
* 2)} is in the high-surrogate range, then the
     
* supplementary code point value of the surrogate pair is
     
* returned. If the {@code char} value at {@code index -
     
* 1} is an unpaired low-surrogate or a high-surrogate, the
     
* surrogate value is returned.
     
*
     
* @paramindex the index following the code point that should be returned
     
* @return
    
the Unicode code point value before the given index.
     
* @exception IndexOutOfBoundsException if the {@code index}
     
*
            
argument is less than 1 or greater than the length
     
*
            
of this sequence.
     
*/

    
public int codePointBefore(int index) {
        
int i = index - 1;
        
if ((i < 0) || (i >= count)) {
            
throw new StringIndexOutOfBoundsException(index);
        
}
        
return Character.codePointBeforeImpl(value, index, 0);
    
}

    
/**
     
* Returns the number of Unicode code points in the specified text
     
* range of this sequence. The text range begins at the specified
     
* {@code beginIndex} and extends to the {@code char} at
     
* index {@code endIndex - 1}. Thus the length (in
     
* {@code char}s) of the text range is
     
* {@code endIndex-beginIndex}. Unpaired surrogates within
     
* this sequence count as one code point each.
     
*
     
* @param beginIndex the index to the first {@code char} of
     
* the text range.
     
* @param endIndex the index after the last {@code char} of
     
* the text range.
     
* @return the number of Unicode code points in the specified text
     
* range
     
* @exception IndexOutOfBoundsException if the
     
* {@code beginIndex} is negative, or {@code endIndex}
     
* is larger than the length of this sequence, or
     
* {@code beginIndex} is larger than {@code endIndex}.
     
*/

    
public int codePointCount(int beginIndex, int endIndex) {
        
if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
            
throw new IndexOutOfBoundsException();
        
}
        
return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex);
    
}

    
/**
     
* Returns the index within this sequence that is offset from the
     
* given {@code index} by {@code codePointOffset} code
     
* points. Unpaired surrogates within the text range given by
     
* {@code index} and {@code codePointOffset} count as
     
* one code point each.
     
*
     
* @param index the index to be offset
     
* @param codePointOffset the offset in code points
     
* @return the index within this sequence
     
* @exception IndexOutOfBoundsException if {@code index}
     
*
   
is negative or larger then the length of this sequence,
     
*
   
or if {@code codePointOffset} is positive and the subsequence
     
*
   
starting with {@code index} has fewer than
     
*
   
{@code codePointOffset} code points,
     
*
   
or if {@code codePointOffset} is negative and the subsequence
     
*
   
before {@code index} has fewer than the absolute value of
     
*
   
{@code codePointOffset} code points.
     
*/

    
public int offsetByCodePoints(int index, int codePointOffset) {
        
if (index < 0 || index > count) {
            
throw new IndexOutOfBoundsException();
        
}
        
return Character.offsetByCodePointsImpl(value, 0, count,
                                                
index, codePointOffset);
    
}

    
/**
     
* Characters are copied from this sequence into the
     
* destination character array {@code dst}. The first character to
     
* be copied is at index {@code srcBegin}; the last character to
     
* be copied is at index {@code srcEnd-1}. The total number of
     
* characters to be copied is {@code srcEnd-srcBegin}. The
     
* characters are copied into the subarray of {@code dst} starting
     
* at index {@code dstBegin} and ending at index:
     
* <pre>{@code
     
* dstbegin + (srcEnd-srcBegin) - 1
     
* }</pre>
     
*
     
* @param
      
srcBegin
   
start copying at this offset.
     
* @param
      
srcEndstop copying at this offset.
     
* @param
      
dst
        
the array to copy the data into.
     
* @param
      
dstBegin
   
offset into {@code dst}.
     
* @throwsIndexOutOfBoundsException
  
if any of the following is true:
     
*
             
<ul>
     
*
             
<li>{@code srcBegin} is negative
     
*
             
<li>{@code dstBegin} is negative
     
*
             
<li>the {@code srcBegin} argument is greater than
     
*
             
the {@code srcEnd} argument.
     
*
             
<li>{@code srcEnd} is greater than
     
*
             
{@code this.length()}.
     
*
             
<li>{@code dstBegin+srcEnd-srcBegin} is greater than
     
*
             
{@code dst.length}
     
*
             
</ul>
     
*/

    
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
    
{
        
if (srcBegin < 0)
            
throw new StringIndexOutOfBoundsException(srcBegin);
        
if ((srcEnd < 0) || (srcEnd > count))
            
throw new StringIndexOutOfBoundsException(srcEnd);
        
if (srcBegin > srcEnd)
            
throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");
        
System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
    
}

    
/**
     
* The character at the specified index is set to {@code ch}. This
     
* sequence is altered to represent a new character sequence that is
     
* identical to the old character sequence, except that it contains the
     
* character {@code ch} at position {@code index}.
     
* <p>
     
* The index argument must be greater than or equal to
     
* {@code 0}, and less than the length of this sequence.
     
*
     
* @param
      
index
   
the index of the character to modify.
     
* @param
      
chthe new character.
     
* @throwsIndexOutOfBoundsException
  
if {@code index} is
     
*
             
negative or greater than or equal to {@code length()}.
     
*/

    
public void setCharAt(int index, char ch) {
        
if ((index < 0) || (index >= count))
            
throw new StringIndexOutOfBoundsException(index);
        
value[index] = ch;
    
}

    
/**
     
* Appends the string representation of the {@code Object} argument.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(Object)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
objan {@code Object}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(Object obj) {
        
return append(String.valueOf(obj));
    
}

    
/**
     
* Appends the specified string to this character sequence.
     
* <p>
     
* The characters of the {@code String} argument are appended, in
     
* order, increasing the length of this sequence by the length of the
     
* argument. If {@code str} is {@code null}, then the four
     
* characters {@code "null"} are appended.
     
* <p>
     
* Let <i>n</i> be the length of this character sequence just prior to
     
* execution of the {@code append} method. Then the character at
     
* index <i>k</i> in the new character sequence is equal to the character
     
* at index <i>k</i> in the old character sequence, if <i>k</i> is less
     
* than <i>n</i>; otherwise, it is equal to the character at index
     
* <i>k-n</i> in the argument {@code str}.
     
*
     
* @param
   
stra string.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(String str) {
        
if (str == null)
            
return appendNull();
        
int len = str.length();
        
ensureCapacityInternal(count + len);
        
str.getChars(0, len, value, count);
        
count += len;
        
return this;
    
}

    
// Documentation in subclasses because of synchro difference
    
public AbstractStringBuilder append(StringBuffer sb) {
        
if (sb == null)
            
return appendNull();
        
int len = sb.length();
        
ensureCapacityInternal(count + len);
        
sb.getChars(0, len, value, count);
        
count += len;
        
return this;
    
}

    
/**
     
* @since 1.8
     
*/
    
AbstractStringBuilder append(AbstractStringBuilder asb) {
        
if (asb == null)
            
return appendNull();
        
int len = asb.length();
        
ensureCapacityInternal(count + len);
        
asb.getChars(0, len, value, count);
        
count += len;
        
return this;
    
}

    
// Documentation in subclasses because of synchro difference
    
@Override
    
public AbstractStringBuilder append(CharSequence s) {
        
if (s == null)
            
return appendNull();
        
if (s instanceof String)
            
return this.append((String)s);
        
if (s instanceof AbstractStringBuilder)
            
return this.append((AbstractStringBuilder)s);

        
return this.append(s, 0, s.length());
    
}

    
private AbstractStringBuilder appendNull() {
        
int c = count;
        
ensureCapacityInternal(c + 4);
        
final char[] value = this.value;
        
value[c++] = 'n';
        
value[c++] = 'u';
        
value[c++] = 'l';
        
value[c++] = 'l';
        
count = c;
        
return this;
    
}

    
/**
     
* Appends a subsequence of the specified {@code CharSequence} to this
     
* sequence.
     
* <p>
     
* Characters of the argument {@code s}, starting at
     
* index {@code start}, are appended, in order, to the contents of
     
* this sequence up to the (exclusive) index {@code end}. The length
     
* of this sequence is increased by the value of {@code end - start}.
     
* <p>
     
* Let <i>n</i> be the length of this character sequence just prior to
     
* execution of the {@code append} method. Then the character at
     
* index <i>k</i> in this character sequence becomes equal to the
     
* character at index <i>k</i> in this sequence, if <i>k</i> is less than
     
* <i>n</i>; otherwise, it is equal to the character at index
     
* <i>k+start-n</i> in the argument {@code s}.
     
* <p>
     
* If {@code s} is {@code null}, then this method appends
     
* characters as if the s parameter was a sequence containing the four
     
* characters {@code "null"}.
     
*
     
* @param
   
s the sequence to append.
     
* @param
   
startthe starting index of the subsequence to be appended.
     
* @param
   
endthe end index of the subsequence to be appended.
     
* @return
  
a reference to this object.
     
* @throwsIndexOutOfBoundsException if
     
*
             
{@code start} is negative, or
     
*
             
{@code start} is greater than {@code end} or
     
*
             
{@code end} is greater than {@code s.length()}
     
*/

    
@Override
    
public AbstractStringBuilder append(CharSequence s, int start, int end) {
        
if (s == null)
            
s = "null";
        
if ((start < 0) || (start > end) || (end > s.length()))
            
throw new IndexOutOfBoundsException(
                
"start " + start + ", end " + end + ", s.length() "
                
+ s.length());
        
int len = end - start;
        
ensureCapacityInternal(count + len);
        
for (int i = start, j = count; i < end; i++, j++)
            
value[j] = s.charAt(i);
        
count += len;
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code char} array
     
* argument to this sequence.
     
* <p>
     
* The characters of the array argument are appended, in order, to
     
* the contents of this sequence. The length of this sequence
     
* increases by the length of the argument.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(char[])},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
strthe characters to be appended.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(char[] str) {
        
int len = str.length;
        
ensureCapacityInternal(count + len);
        
System.arraycopy(str, 0, value, count, len);
        
count += len;
        
return this;
    
}

    
/**
     
* Appends the string representation of a subarray of the
     
* {@code char} array argument to this sequence.
     
* <p>
     
* Characters of the {@code char} array {@code str}, starting at
     
* index {@code offset}, are appended, in order, to the contents
     
* of this sequence. The length of this sequence increases
     
* by the value of {@code len}.
     
* <p>
     
* The overall effect is exactly as if the arguments were converted
     
* to a string by the method {@link String#valueOf(char[],int,int)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
str
      
the characters to be appended.
     
* @param
   
offsetthe index of the first {@code char} to append.
     
* @param
   
len
      
the number of {@code char}s to append.
     
* @return
  
a reference to this object.
     
* @throws IndexOutOfBoundsException
     
*
         
if {@code offset < 0} or {@code len < 0}
     
*
         
or {@code offset+len > str.length}
     
*/

    
public AbstractStringBuilder append(char str[], int offset, int len) {
        
if (len > 0)
                
// let arraycopy report AIOOBE for len < 0
            
ensureCapacityInternal(count + len);
        
System.arraycopy(str, offset, value, count, len);
        
count += len;
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code boolean}
     
* argument to the sequence.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(boolean)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
ba {@code boolean}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(boolean b) {
        
if (b) {
            
ensureCapacityInternal(count + 4);
            
value[count++] = 't';
            
value[count++] = 'r';
            
value[count++] = 'u';
            
value[count++] = 'e';
        
} else {
            
ensureCapacityInternal(count + 5);
            
value[count++] = 'f';
            
value[count++] = 'a';
            
value[count++] = 'l';
            
value[count++] = 's';
            
value[count++] = 'e';
        
}
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code char}
     
* argument to this sequence.
     
* <p>
     
* The argument is appended to the contents of this sequence.
     
* The length of this sequence increases by {@code 1}.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(char)},
     
* and the character in that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
ca {@code char}.
     
* @return
  
a reference to this object.
     
*/

    
@Override
    
public AbstractStringBuilder append(char c) {
        
ensureCapacityInternal(count + 1);
        
value[count++] = c;
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code int}
     
* argument to this sequence.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(int)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
ian {@code int}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(int i) {
        
if (i == Integer.MIN_VALUE) {
            
append("-2147483648");
            
return this;
        
}
        
int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1
                                     
: Integer.stringSize(i);
        
int spaceNeeded = count + appendedLength;
        
ensureCapacityInternal(spaceNeeded);
        
Integer.getChars(i, spaceNeeded, value);
        
count = spaceNeeded;
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code long}
     
* argument to this sequence.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(long)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
la {@code long}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(long l) {
        
if (l == Long.MIN_VALUE) {
            
append("-9223372036854775808");
            
return this;
        
}
        
int appendedLength = (l < 0) ? Long.stringSize(-l) + 1
                                     
: Long.stringSize(l);
        
int spaceNeeded = count + appendedLength;
        
ensureCapacityInternal(spaceNeeded);
        
Long.getChars(l, spaceNeeded, value);
        
count = spaceNeeded;
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code float}
     
* argument to this sequence.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(float)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
fa {@code float}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(float f) {
        
FloatingDecimal.appendTo(f,this);
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code double}
     
* argument to this sequence.
     
* <p>
     
* The overall effect is exactly as if the argument were converted
     
* to a string by the method {@link String#valueOf(double)},
     
* and the characters of that string were then
     
* {@link #append(String) appended} to this character sequence.
     
*
     
* @param
   
da {@code double}.
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder append(double d) {
        
FloatingDecimal.appendTo(d,this);
        
return this;
    
}

    
/**
     
* Removes the characters in a substring of this sequence.
     
* The substring begins at the specified {@code start} and extends to
     
* the character at index {@code end - 1} or to the end of the
     
* sequence if no such character exists. If
     
* {@code start} is equal to {@code end}, no changes are made.
     
*
     
* @param
      
start
  
The beginning index, inclusive.
     
* @param
      
end
    
The ending index, exclusive.
     
* @returnThis object.
     
* @throwsStringIndexOutOfBoundsException
  
if {@code start}
     
*
             
is negative, greater than {@code length()}, or
     
*
             
greater than {@code end}.
     
*/

    
public AbstractStringBuilder delete(int start, int end) {
        
if (start < 0)
            
throw new StringIndexOutOfBoundsException(start);
        
if (end > count)
            
end = count;
        
if (start > end)
            
throw new StringIndexOutOfBoundsException();
        
int len = end - start;
        
if (len > 0) {
            
System.arraycopy(value, start+len, value, start, count-end);
            
count -= len;
        
}
        
return this;
    
}

    
/**
     
* Appends the string representation of the {@code codePoint}
     
* argument to this sequence.
     
*
     
* <p> The argument is appended to the contents of this sequence.
     
* The length of this sequence increases by
     
* {@link Character#charCount(int) Character.charCount(codePoint)}.
     
*
     
* <p> The overall effect is exactly as if the argument were
     
* converted to a {@code char} array by the method
     
* {@link Character#toChars(int)} and the character in that array
     
* were then {@link #append(char[]) appended} to this character
     
* sequence.
     
*
     
* @param
   
codePointa Unicode code point
     
* @return
  
a reference to this object.
     
* @exception IllegalArgumentException if the specified
     
* {@code codePoint} isn't a valid Unicode code point
     
*/

    
public AbstractStringBuilder appendCodePoint(int codePoint) {
        
final int count = this.count;

        
if (Character.isBmpCodePoint(codePoint)) {
            
ensureCapacityInternal(count + 1);
            
value[count] = (char) codePoint;
            
this.count = count + 1;
        
} else if (Character.isValidCodePoint(codePoint)) {
            
ensureCapacityInternal(count + 2);
            
Character.toSurrogates(codePoint, value, count);
            
this.count = count + 2;
        
} else {
            
throw new IllegalArgumentException();
        
}
        
return this;
    
}

    
/**
     
* Removes the {@code char} at the specified position in this
     
* sequence. This sequence is shortened by one {@code char}.
     
*
     
* <p>Note: If the character at the given index is a supplementary
     
* character, this method does not remove the entire character. If
     
* correct handling of supplementary characters is required,
     
* determine the number of {@code char}s to remove by calling
     
* {@code Character.charCount(thisSequence.codePointAt(index))},
     
* where {@code thisSequence} is this sequence.
     
*
     
* @param
       
index
  
Index of {@code char} to remove
     
* @return
      
This object.
     
* @throws
      
StringIndexOutOfBoundsException
  
if the {@code index}
     
*
              
is negative or greater than or equal to
     
*
              
{@code length()}.
     
*/

    
public AbstractStringBuilder deleteCharAt(int index) {
        
if ((index < 0) || (index >= count))
            
throw new StringIndexOutOfBoundsException(index);
        
System.arraycopy(value, index+1, value, index, count-index-1);
        
count--;
        
return this;
    
}

    
/**
     
* Replaces the characters in a substring of this sequence
     
* with characters in the specified {@code String}. The substring
     
* begins at the specified {@code start} and extends to the character
     
* at index {@code end - 1} or to the end of the
     
* sequence if no such character exists. First the
     
* characters in the substring are removed and then the specified
     
* {@code String} is inserted at {@code start}. (This
     
* sequence will be lengthened to accommodate the
     
* specified String if necessary.)
     
*
     
* @param
      
start
    
The beginning index, inclusive.
     
* @param
      
endThe ending index, exclusive.
     
* @param
      
str
   
String that will replace previous contents.
     
* @returnThis object.
     
* @throwsStringIndexOutOfBoundsException
  
if {@code start}
     
*
             
is negative, greater than {@code length()}, or
     
*
             
greater than {@code end}.
     
*/

    
public AbstractStringBuilder replace(int start, int end, String str) {
        
if (start < 0)
            
throw new StringIndexOutOfBoundsException(start);
        
if (start > count)
            
throw new StringIndexOutOfBoundsException("start > length()");
        
if (start > end)
            
throw new StringIndexOutOfBoundsException("start > end");

        
if (end > count)
            
end = count;
        
int len = str.length();
        
int newCount = count + len - (end - start);
        
ensureCapacityInternal(newCount);

        
System.arraycopy(value, end, value, start + len, count - end);
        
str.getChars(value, start);
        
count = newCount;
        
return this;
    
}

    
/**
     
* Returns a new {@code String} that contains a subsequence of
     
* characters currently contained in this character sequence. The
     
* substring begins at the specified index and extends to the end of
     
* this sequence.
     
*
     
* @param
      
start
    
The beginning index, inclusive.
     
* @returnThe new string.
     
* @throwsStringIndexOutOfBoundsException
  
if {@code start} is
     
*
             
less than zero, or greater than the length of this object.
     
*/

    
public String substring(int start) {
        
return substring(start, count);
    
}

    
/**
     
* Returns a new character sequence that is a subsequence of this sequence.
     
*
     
* <p> An invocation of this method of the form
     
*
     
* <pre>{@code
     
* sb.subSequence(begin,&nbsp;end)}</pre>
     
*
     
* behaves in exactly the same way as the invocation
     
*
     
* <pre>{@code
     
* sb.substring(begin,&nbsp;end)}</pre>
     
*
     
* This method is provided so that this class can
     
* implement the {@link CharSequence} interface.
     
*
     
* @param
      
start
   
the start index, inclusive.
     
* @param
      
endthe end index, exclusive.
     
* @returnthe specified subsequence.
     
*
     
* @throws
  
IndexOutOfBoundsException
     
*
          
if {@code start} or {@code end} are negative,
     
*
          
if {@code end} is greater than {@code length()},
     
*
          
or if {@code start} is greater than {@code end}
     
* @spec JSR-51
     
*/

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

    
/**
     
* Returns a new {@code String} that contains a subsequence of
     
* characters currently contained in this sequence. The
     
* substring begins at the specified {@code start} and
     
* extends to the character at index {@code end - 1}.
     
*
     
* @param
      
start
    
The beginning index, inclusive.
     
* @param
      
endThe ending index, exclusive.
     
* @returnThe new string.
     
* @throwsStringIndexOutOfBoundsException
  
if {@code start}
     
*
             
or {@code end} are negative or greater than
     
*
             
{@code length()}, or {@code start} is
     
*
             
greater than {@code end}.
     
*/

    
public String substring(int start, int end) {
        
if (start < 0)
            
throw new StringIndexOutOfBoundsException(start);
        
if (end > count)
            
throw new StringIndexOutOfBoundsException(end);
        
if (start > end)
            
throw new StringIndexOutOfBoundsException(end - start);
        
return new String(value, start, end - start);
    
}

    
/**
     
* Inserts the string representation of a subarray of the {@code str}
     
* array argument into this sequence. The subarray begins at the
     
* specified {@code offset} and extends {@code len} {@code char}s.
     
* The characters of the subarray are inserted into this sequence at
     
* the position indicated by {@code index}. The length of this
     
* sequence increases by {@code len} {@code char}s.
     
*
     
* @param
      
index
    
position at which to insert subarray.
     
* @param
      
str
       
A {@code char} array.
     
* @param
      
offset
   
the index of the first {@code char} in subarray to
     
*
             
be inserted.
     
* @param
      
lenthe number of {@code char}s in the subarray to
     
*
             
be inserted.
     
* @returnThis object
     
* @throwsStringIndexOutOfBoundsException
  
if {@code index}
     
*
             
is negative or greater than {@code length()}, or
     
*
             
{@code offset} or {@code len} are negative, or
     
*
             
{@code (offset+len)} is greater than
     
*
             
{@code str.length}.
     
*/

    
public AbstractStringBuilder insert(int index, char[] str, int offset,
                                        
int len)
    
{
        
if ((index < 0) || (index > length()))
            
throw new StringIndexOutOfBoundsException(index);
        
if ((offset < 0) || (len < 0) || (offset > str.length - len))
            
throw new StringIndexOutOfBoundsException(
                
"offset " + offset + ", len " + len + ", str.length "
                
+ str.length);
        
ensureCapacityInternal(count + len);
        
System.arraycopy(value, index, value, index + len, count - index);
        
System.arraycopy(str, offset, value, index, len);
        
count += len;
        
return this;
    
}

    
/**
     
* Inserts the string representation of the {@code Object}
     
* argument into this character sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(Object)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
objan {@code Object}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, Object obj) {
        
return insert(offset, String.valueOf(obj));
    
}

    
/**
     
* Inserts the string into this character sequence.
     
* <p>
     
* The characters of the {@code String} argument are inserted, in
     
* order, into this sequence at the indicated offset, moving up any
     
* characters originally above that position and increasing the length
     
* of this sequence by the length of the argument. If
     
* {@code str} is {@code null}, then the four characters
     
* {@code "null"} are inserted into this sequence.
     
* <p>
     
* The character at index <i>k</i> in the new character sequence is
     
* equal to:
     
* <ul>
     
* <li>the character at index <i>k</i> in the old character sequence, if
     
* <i>k</i> is less than {@code offset}
     
* <li>the character at index <i>k</i>{@code -offset} in the
     
* argument {@code str}, if <i>k</i> is not less than
     
* {@code offset} but is less than {@code offset+str.length()}
     
* <li>the character at index <i>k</i>{@code -str.length()} in the
     
* old character sequence, if <i>k</i> is not less than
     
* {@code offset+str.length()}
     
* </ul><p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
stra string.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, String str) {
        
if ((offset < 0) || (offset > length()))
            
throw new StringIndexOutOfBoundsException(offset);
        
if (str == null)
            
str = "null";
        
int len = str.length();
        
ensureCapacityInternal(count + len);
        
System.arraycopy(value, offset, value, offset + len, count - offset);
        
str.getChars(value, offset);
        
count += len;
        
return this;
    
}

    
/**
     
* Inserts the string representation of the {@code char} array
     
* argument into this sequence.
     
* <p>
     
* The characters of the array argument are inserted into the
     
* contents of this sequence at the position indicated by
     
* {@code offset}. The length of this sequence increases by
     
* the length of the argument.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(char[])},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
stra character array.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, char[] str) {
        
if ((offset < 0) || (offset > length()))
            
throw new StringIndexOutOfBoundsException(offset);
        
int len = str.length;
        
ensureCapacityInternal(count + len);
        
System.arraycopy(value, offset, value, offset + len, count - offset);
        
System.arraycopy(str, 0, value, offset, len);
        
count += len;
        
return this;
    
}

    
/**
     
* Inserts the specified {@code CharSequence} into this sequence.
     
* <p>
     
* The characters of the {@code CharSequence} argument are inserted,
     
* in order, into this sequence at the indicated offset, moving up
     
* any characters originally above that position and increasing the length
     
* of this sequence by the length of the argument s.
     
* <p>
     
* The result of this method is exactly the same as if it were an
     
* invocation of this object's
     
* {@link #insert(int,CharSequence,int,int) insert}(dstOffset, s, 0, s.length())
     
* method.
     
*
     
* <p>If {@code s} is {@code null}, then the four characters
     
* {@code "null"} are inserted into this sequence.
     
*
     
* @param
      
dstOffset
   
the offset.
     
* @param
      
s the sequence to be inserted
     
* @returna reference to this object.
     
* @throwsIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
        
if (s == null)
            
s = "null";
        
if (s instanceof String)
            
return this.insert(dstOffset, (String)s);
        
return this.insert(dstOffset, s, 0, s.length());
    
}

    
/**
     
* Inserts a subsequence of the specified {@code CharSequence} into
     
* this sequence.
     
* <p>
     
* The subsequence of the argument {@code s} specified by
     
* {@code start} and {@code end} are inserted,
     
* in order, into this sequence at the specified destination offset, moving
     
* up any characters originally above that position. The length of this
     
* sequence is increased by {@code end - start}.
     
* <p>
     
* The character at index <i>k</i> in this sequence becomes equal to:
     
* <ul>
     
* <li>the character at index <i>k</i> in this sequence, if
     
* <i>k</i> is less than {@code dstOffset}
     
* <li>the character at index <i>k</i>{@code +start-dstOffset} in
     
* the argument {@code s}, if <i>k</i> is greater than or equal to
     
* {@code dstOffset} but is less than {@code dstOffset+end-start}
     
* <li>the character at index <i>k</i>{@code -(end-start)} in this
     
* sequence, if <i>k</i> is greater than or equal to
     
* {@code dstOffset+end-start}
     
* </ul><p>
     
* The {@code dstOffset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
* <p>The start argument must be nonnegative, and not greater than
     
* {@code end}.
     
* <p>The end argument must be greater than or equal to
     
* {@code start}, and less than or equal to the length of s.
     
*
     
* <p>If {@code s} is {@code null}, then this method inserts
     
* characters as if the s parameter was a sequence containing the four
     
* characters {@code "null"}.
     
*
     
* @param
      
dstOffset
   
the offset in this sequence.
     
* @param
      
s
       
the sequence to be inserted.
     
* @param
      
start
   
the starting index of the subsequence to be inserted.
     
* @param
      
endthe end index of the subsequence to be inserted.
     
* @returna reference to this object.
     
* @throwsIndexOutOfBoundsException
  
if {@code dstOffset}
     
*
             
is negative or greater than {@code this.length()}, or
     
*
              
{@code start} or {@code end} are negative, or
     
*
              
{@code start} is greater than {@code end} or
     
*
              
{@code end} is greater than {@code s.length()}
     
*/

     
public AbstractStringBuilder insert(int dstOffset, CharSequence s,
                                         
int start, int end) {
        
if (s == null)
            
s = "null";
        
if ((dstOffset < 0) || (dstOffset > this.length()))
            
throw new IndexOutOfBoundsException("dstOffset "+dstOffset);
        
if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))
            
throw new IndexOutOfBoundsException(
                
"start " + start + ", end " + end + ", s.length() "
                
+ s.length());
        
int len = end - start;
        
ensureCapacityInternal(count + len);
        
System.arraycopy(value, dstOffset, value, dstOffset + len,
                         
count - dstOffset);
        
for (int i=start; i<end; i++)
            
value[dstOffset++] = s.charAt(i);
        
count += len;
        
return this;
    
}

    
/**
     
* Inserts the string representation of the {@code boolean}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(boolean)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
b
        
a {@code boolean}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, boolean b) {
        
return insert(offset, String.valueOf(b));
    
}

    
/**
     
* Inserts the string representation of the {@code char}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(char)},
     
* and the character in that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
c
        
a {@code char}.
     
* @returna reference to this object.
     
* @throwsIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, char c) {
        
ensureCapacityInternal(count + 1);
        
System.arraycopy(value, offset, value, offset + 1, count - offset);
        
value[offset] = c;
        
count += 1;
        
return this;
    
}

    
/**
     
* Inserts the string representation of the second {@code int}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(int)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
i
        
an {@code int}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, int i) {
        
return insert(offset, String.valueOf(i));
    
}

    
/**
     
* Inserts the string representation of the {@code long}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(long)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
l
        
a {@code long}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, long l) {
        
return insert(offset, String.valueOf(l));
    
}

    
/**
     
* Inserts the string representation of the {@code float}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(float)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
f
        
a {@code float}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, float f) {
        
return insert(offset, String.valueOf(f));
    
}

    
/**
     
* Inserts the string representation of the {@code double}
     
* argument into this sequence.
     
* <p>
     
* The overall effect is exactly as if the second argument were
     
* converted to a string by the method {@link String#valueOf(double)},
     
* and the characters of that string were then
     
* {@link #insert(int,String) inserted} into this character
     
* sequence at the indicated offset.
     
* <p>
     
* The {@code offset} argument must be greater than or equal to
     
* {@code 0}, and less than or equal to the {@linkplain #length() length}
     
* of this sequence.
     
*
     
* @param
      
offset
   
the offset.
     
* @param
      
d
        
a {@code double}.
     
* @returna reference to this object.
     
* @throwsStringIndexOutOfBoundsException
  
if the offset is invalid.
     
*/

    
public AbstractStringBuilder insert(int offset, double d) {
        
return insert(offset, String.valueOf(d));
    
}

    
/**
     
* 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:
     
* <pre>{@code
     
* this.toString().startsWith(str, <i>k</i>)
     
* }</pre>
     
* is {@code true}.
     
*
     
* @param
   
strany 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} is returned.
     
*/

    
public int indexOf(String str) {
        
return indexOf(str, 0);
    
}

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

    
public int indexOf(String str, int fromIndex) {
        
return String.indexOf(value, 0, count, str, fromIndex);
    
}

    
/**
     
* 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()}.
     
* The returned index is the largest value <i>k</i> such that
     
* <pre>{@code
     
* this.toString().startsWith(str, k)
     
* }</pre>
     
* is true.
     
*
     
* @param
   
strthe 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} is returned.
     
*/

    
public int lastIndexOf(String str) {
        
return lastIndexOf(str, count);
    
}

    
/**
     
* Returns the index within this string of the last occurrence of the
     
* specified substring. The integer returned is the largest value <i>k</i>
     
* such that:
     
* <pre>{@code
     
*k <= Math.min(fromIndex, this.length()) &&
     
*
                   
this.toString().startsWith(str, k)
     
* }</pre>
     
* If no such value of <i>k</i> exists, then -1 is returned.
     
*
     
* @param
   
str
         
the substring to search for.
     
* @param
   
fromIndexthe index to start the search from.
     
* @return
  
the index within this sequence of the last occurrence of the
     
*
          
specified substring.
     
*/

    
public int lastIndexOf(String str, int fromIndex) {
        
return String.lastIndexOf(value, 0, count, str, fromIndex);
    
}

    
/**
     
* Causes this character sequence to be replaced by the reverse of
     
* the sequence. If there are any surrogate pairs included in the
     
* sequence, these are treated as single characters for the
     
* reverse operation. Thus, the order of the high-low surrogates
     
* is never reversed.
     
*
     
* Let <i>n</i> be the character length of this character sequence
     
* (not the length in {@code char} values) just prior to
     
* execution of the {@code reverse} method. Then the
     
* character at index <i>k</i> in the new character sequence is
     
* equal to the character at index <i>n-k-1</i> in the old
     
* character sequence.
     
*
     
* <p>Note that the reverse operation may result in producing
     
* surrogate pairs that were unpaired low-surrogates and
     
* high-surrogates before the operation. For example, reversing
     
* "\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
     
* a valid surrogate pair.
     
*
     
* @return
  
a reference to this object.
     
*/

    
public AbstractStringBuilder reverse() {
        
boolean hasSurrogates = false;
        
int n = count - 1;
        
for (int j = (n-1) >> 1; j >= 0; j--) {
            
int k = n - j;
            
char cj = value[j];
            
char ck = value[k];
            
value[j] = ck;
            
value[k] = cj;
            
if (Character.isSurrogate(cj) ||
                
Character.isSurrogate(ck)) {
                
hasSurrogates = true;
            
}
        
}
        
if (hasSurrogates) {
            
reverseAllValidSurrogatePairs();
        
}
        
return this;
    
}

    
/** Outlined helper method for reverse() */
    
private void reverseAllValidSurrogatePairs() {
        
for (int i = 0; i < count - 1; i++) {
            
char c2 = value[i];
            
if (Character.isLowSurrogate(c2)) {
                
char c1 = value[i + 1];
                
if (Character.isHighSurrogate(c1)) {
                    
value[i++] = c1;
                    
value[i] = c2;
                
}
            
}
        
}
    
}

    
/**
     
* Returns a string representing the data in this sequence.
     
* A new {@code String} object is allocated and initialized to
     
* contain the character sequence currently represented by this
     
* object. This {@code String} is then returned. Subsequent
     
* changes to this sequence do not affect the contents of the
     
* {@code String}.
     
*
     
* @return
  
a string representation of this sequence of characters.
     
*/

    
@Override
    
public abstract String toString();

    
/**
     
* Needed by {@code String} for the contentEquals method.
     
*/

    
final char[] getValue() {
        
return value;
    
}

}