/*
 
* Copyright (c) 1994, 2013, 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 java.util.Arrays;

/**
 
* A thread-safe, mutable sequence of characters.
 
* A string buffer is like a {@link String}, but can be modified. 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>
 
* String buffers are safe for use by multiple threads. The methods
 
* are synchronized where necessary so that all the operations on any
 
* particular instance behave as if they occur in some serial order
 
* that is consistent with the order of the method calls made by each of
 
* the individual threads involved.
 
* <p>
 
* The principal operations on a {@code StringBuffer} are the
 
* {@code append} and {@code insert} methods, which are
 
* overloaded so as to accept data of any type. Each effectively
 
* converts a given datum to a string and then appends or inserts the
 
* characters of that string to the string buffer. The
 
* {@code append} method always adds these characters at the end
 
* of the buffer; the {@code insert} method adds the characters at
 
* a specified point.
 
* <p>
 
* For example, if {@code z} refers to a string buffer object
 
* whose current contents are {@code "start"}, then
 
* the method call {@code z.append("le")} would cause the string
 
* buffer to contain {@code "startle"}, whereas
 
* {@code z.insert(4, "le")} would alter the string buffer to
 
* contain {@code "starlet"}.
 
* <p>
 
* In general, if sb refers to an instance of a {@code StringBuffer},
 
* then {@code sb.append(x)} has the same effect as
 
* {@code sb.insert(sb.length(), x)}.
 
* <p>
 
* Whenever an operation occurs involving a source sequence (such as
 
* appending or inserting from a source sequence), this class synchronizes
 
* only on the string buffer performing the operation, not on the source.
 
* Note that while {@code StringBuffer} is designed to be safe to use
 
* concurrently from multiple threads, if the constructor or the
 
* {@code append} or {@code insert} operation is passed a source sequence
 
* that is shared across threads, the calling code must ensure
 
* that the operation has a consistent and unchanging view of the source
 
* sequence for the duration of the operation.
 
* This could be satisfied by the caller holding a lock during the
 
* operation's call, by using an immutable source sequence, or by not
 
* sharing the source sequence across threads.
 
* <p>
 
* Every string buffer has a capacity. As long as the length of the
 
* character sequence contained in the string buffer does not exceed
 
* the capacity, it is not necessary to allocate a new internal
 
* buffer array. If the internal buffer overflows, it is
 
* automatically made larger.
 
* <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.
 
* <p>
 
* As of
  
release JDK 5, this class has been supplemented with an equivalent
 
* class designed for use by a single thread, {@link StringBuilder}.
  
The
 
* {@code StringBuilder} class should generally be used in preference to
 
* this one, as it supports all of the same operations but it is faster, as
 
* it performs no synchronization.
 
*
 
* @author
      
Arthur van Hoff
 
* @see
     
java.lang.StringBuilder
 
* @see
     
java.lang.String
 
* @since
   
JDK1.0
 
*/

public final class StringBuffer
    
extends AbstractStringBuilder
    
implements java.io.Serializable, CharSequence
{

    
/**
     
* A cache of the last value returned by toString. Cleared
     
* whenever the StringBuffer is modified.
     
*/

    
private transient char[] toStringCache;

    
/** use serialVersionUID from JDK 1.0.2 for interoperability */
    
static final long serialVersionUID = 3388685877147921107L;

    
/**
     
* Constructs a string buffer with no characters in it and an
     
* initial capacity of 16 characters.
     
*/

    
public StringBuffer() {
        
super(16);
    
}

    
/**
     
* Constructs a string buffer with no characters in it and
     
* the specified initial capacity.
     
*
     
* @param
      
capacity
  
the initial capacity.
     
* @exception
  
NegativeArraySizeExceptionif the {@code capacity}
     
*
               
argument is less than {@code 0}.
     
*/

    
public StringBuffer(int capacity) {
        
super(capacity);
    
}

    
/**
     
* Constructs a string buffer initialized to the contents of the
     
* specified string. The initial capacity of the string buffer is
     
* {@code 16} plus the length of the string argument.
     
*
     
* @param
   
strthe initial contents of the buffer.
     
*/

    
public StringBuffer(String str) {
        
super(str.length() + 16);
        
append(str);
    
}

    
/**
     
* Constructs a string buffer that contains the same characters
     
* as the specified {@code CharSequence}. The initial capacity of
     
* the string buffer is {@code 16} plus the length of the
     
* {@code CharSequence} argument.
     
* <p>
     
* If the length of the specified {@code CharSequence} is
     
* less than or equal to zero, then an empty buffer of capacity
     
* {@code 16} is returned.
     
*
     
* @param
      
seq
   
the sequence to copy.
     
* @since 1.5
     
*/

    
public StringBuffer(CharSequence seq) {
        
this(seq.length() + 16);
        
append(seq);
    
}

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

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


    
@Override
    
public synchronized void ensureCapacity(int minimumCapacity) {
        
super.ensureCapacity(minimumCapacity);
    
}

    
/**
     
* @since
      
1.5
     
*/
    
@Override
    
public synchronized void trimToSize() {
        
super.trimToSize();
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @see
        
#length()
     
*/
    
@Override
    
public synchronized void setLength(int newLength) {
        
toStringCache = null;
        
super.setLength(newLength);
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @see
        
#length()
     
*/
    
@Override
    
public synchronized char charAt(int index) {
        
if ((index < 0) || (index >= count))
            
throw new StringIndexOutOfBoundsException(index);
        
return value[index];
    
}

    
/**
     
* @since
      
1.5
     
*/
    
@Override
    
public synchronized int codePointAt(int index) {
        
return super.codePointAt(index);
    
}

    
/**
     
* @since1.5
     
*/
    
@Override
    
public synchronized int codePointBefore(int index) {
        
return super.codePointBefore(index);
    
}

    
/**
     
* @since1.5
     
*/
    
@Override
    
public synchronized int codePointCount(int beginIndex, int endIndex) {
        
return super.codePointCount(beginIndex, endIndex);
    
}

    
/**
     
* @since1.5
     
*/
    
@Override
    
public synchronized int offsetByCodePoints(int index, int codePointOffset) {
        
return super.offsetByCodePoints(index, codePointOffset);
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
                                      
int dstBegin)
    
{
        
super.getChars(srcBegin, srcEnd, dst, dstBegin);
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @see
        
#length()
     
*/
    
@Override
    
public synchronized void setCharAt(int index, char ch) {
        
if ((index < 0) || (index >= count))
            
throw new StringIndexOutOfBoundsException(index);
        
toStringCache = null;
        
value[index] = ch;
    
}

    
@Override
    
public synchronized StringBuffer append(Object obj) {
        
toStringCache = null;
        
super.append(String.valueOf(obj));
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(String str) {
        
toStringCache = null;
        
super.append(str);
        
return this;
    
}

    
/**
     
* Appends the specified {@code StringBuffer} to this sequence.
     
* <p>
     
* The characters of the {@code StringBuffer} argument are appended,
     
* in order, to the contents of this {@code StringBuffer}, increasing the
     
* length of this {@code StringBuffer} by the length of the argument.
     
* If {@code sb} is {@code null}, then the four characters
     
* {@code "null"} are appended to this {@code StringBuffer}.
     
* <p>
     
* Let <i>n</i> be the length of the old character sequence, the one
     
* contained in the {@code StringBuffer} 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 sb}.
     
* <p>
     
* This method synchronizes on {@code this}, the destination
     
* object, but does not synchronize on the source ({@code sb}).
     
*
     
* @param
   
sbthe {@code StringBuffer} to append.
     
* @return
  
a reference to this object.
     
* @since 1.4
     
*/

    
public synchronized StringBuffer append(StringBuffer sb) {
        
toStringCache = null;
        
super.append(sb);
        
return this;
    
}

    
/**
     
* @since 1.8
     
*/
    
@Override
    
synchronized StringBuffer append(AbstractStringBuilder asb) {
        
toStringCache = null;
        
super.append(asb);
        
return this;
    
}

    
/**
     
* Appends the specified {@code CharSequence} to this
     
* sequence.
     
* <p>
     
* The characters of the {@code CharSequence} argument are appended,
     
* in order, increasing the length of this sequence by the length of the
     
* argument.
     
*
     
* <p>The result of this method is exactly the same as if it were an
     
* invocation of this.append(s, 0, s.length());
     
*
     
* <p>This method synchronizes on {@code this}, the destination
     
* object, but does not synchronize on the source ({@code s}).
     
*
     
* <p>If {@code s} is {@code null}, then the four characters
     
* {@code "null"} are appended.
     
*
     
* @param
   
s the {@code CharSequence} to append.
     
* @return
  
a reference to this object.
     
* @since 1.5
     
*/

    
@Override
    
public synchronized StringBuffer append(CharSequence s) {
        
toStringCache = null;
        
super.append(s);
        
return this;
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.5
     
*/
    
@Override
    
public synchronized StringBuffer append(CharSequence s, int start, int end)
    
{
        
toStringCache = null;
        
super.append(s, start, end);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(char[] str) {
        
toStringCache = null;
        
super.append(str);
        
return this;
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized StringBuffer append(char[] str, int offset, int len) {
        
toStringCache = null;
        
super.append(str, offset, len);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(boolean b) {
        
toStringCache = null;
        
super.append(b);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(char c) {
        
toStringCache = null;
        
super.append(c);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(int i) {
        
toStringCache = null;
        
super.append(i);
        
return this;
    
}

    
/**
     
* @since 1.5
     
*/
    
@Override
    
public synchronized StringBuffer appendCodePoint(int codePoint) {
        
toStringCache = null;
        
super.appendCodePoint(codePoint);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(long lng) {
        
toStringCache = null;
        
super.append(lng);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(float f) {
        
toStringCache = null;
        
super.append(f);
        
return this;
    
}

    
@Override
    
public synchronized StringBuffer append(double d) {
        
toStringCache = null;
        
super.append(d);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized StringBuffer delete(int start, int end) {
        
toStringCache = null;
        
super.delete(start, end);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized StringBuffer deleteCharAt(int index) {
        
toStringCache = null;
        
super.deleteCharAt(index);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized StringBuffer replace(int start, int end, String str) {
        
toStringCache = null;
        
super.replace(start, end, str);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized String substring(int start) {
        
return substring(start, count);
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.4
     
*/
    
@Override
    
public synchronized CharSequence subSequence(int start, int end) {
        
return super.substring(start, end);
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized String substring(int start, int end) {
        
return super.substring(start, end);
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.2
     
*/
    
@Override
    
public synchronized StringBuffer insert(int index, char[] str, int offset,
                                            
int len)
    
{
        
toStringCache = null;
        
super.insert(index, str, offset, len);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized StringBuffer insert(int offset, Object obj) {
        
toStringCache = null;
        
super.insert(offset, String.valueOf(obj));
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized StringBuffer insert(int offset, String str) {
        
toStringCache = null;
        
super.insert(offset, str);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized StringBuffer insert(int offset, char[] str) {
        
toStringCache = null;
        
super.insert(offset, str);
        
return this;
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.5
     
*/
    
@Override
    
public StringBuffer insert(int dstOffset, CharSequence s) {
        
// Note, synchronization achieved via invocations of other StringBuffer methods
        
// after narrowing of s to specific type
        
// Ditto for toStringCache clearing
        
super.insert(dstOffset, s);
        
return this;
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
* @since
      
1.5
     
*/
    
@Override
    
public synchronized StringBuffer insert(int dstOffset, CharSequence s,
            
int start, int end)
    
{
        
toStringCache = null;
        
super.insert(dstOffset, s, start, end);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public
  
StringBuffer insert(int offset, boolean b) {
        
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
        
// after conversion of b to String by super class method
        
// Ditto for toStringCache clearing
        
super.insert(offset, b);
        
return this;
    
}

    
/**
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public synchronized StringBuffer insert(int offset, char c) {
        
toStringCache = null;
        
super.insert(offset, c);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public StringBuffer insert(int offset, int i) {
        
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
        
// after conversion of i to String by super class method
        
// Ditto for toStringCache clearing
        
super.insert(offset, i);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public StringBuffer insert(int offset, long l) {
        
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
        
// after conversion of l to String by super class method
        
// Ditto for toStringCache clearing
        
super.insert(offset, l);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public StringBuffer insert(int offset, float f) {
        
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
        
// after conversion of f to String by super class method
        
// Ditto for toStringCache clearing
        
super.insert(offset, f);
        
return this;
    
}

    
/**
     
* @throws StringIndexOutOfBoundsException {@inheritDoc}
     
*/
    
@Override
    
public StringBuffer insert(int offset, double d) {
        
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
        
// after conversion of d to String by super class method
        
// Ditto for toStringCache clearing
        
super.insert(offset, d);
        
return this;
    
}

    
/**
     
* @since
      
1.4
     
*/
    
@Override
    
public int indexOf(String str) {
        
// Note, synchronization achieved via invocations of other StringBuffer methods
        
return super.indexOf(str);
    
}

    
/**
     
* @since
      
1.4
     
*/
    
@Override
    
public synchronized int indexOf(String str, int fromIndex) {
        
return super.indexOf(str, fromIndex);
    
}

    
/**
     
* @since
      
1.4
     
*/
    
@Override
    
public int lastIndexOf(String str) {
        
// Note, synchronization achieved via invocations of other StringBuffer methods
        
return lastIndexOf(str, count);
    
}

    
/**
     
* @since
      
1.4
     
*/
    
@Override
    
public synchronized int lastIndexOf(String str, int fromIndex) {
        
return super.lastIndexOf(str, fromIndex);
    
}

    
/**
     
* @since
   
JDK1.0.2
     
*/
    
@Override
    
public synchronized StringBuffer reverse() {
        
toStringCache = null;
        
super.reverse();
        
return this;
    
}

    
@Override
    
public synchronized String toString() {
        
if (toStringCache == null) {
            
toStringCache = Arrays.copyOfRange(value, 0, count);
        
}
        
return new String(toStringCache, true);
    
}

    
/**
     
* Serializable fields for StringBuffer.
     
*
     
* @serialField value
  
char[]
     
*
              
The backing character array of this StringBuffer.
     
* @serialField count int
     
*
              
The number of characters in this StringBuffer.
     
* @serialField shared
  
boolean
     
*
              
A flag indicating whether the backing array is shared.
     
*
              
The value is ignored upon deserialization.
     
*/

    
private static final java.io.ObjectStreamField[] serialPersistentFields =
    
{
        
new java.io.ObjectStreamField("value", char[].class),
        
new java.io.ObjectStreamField("count", Integer.TYPE),
        
new java.io.ObjectStreamField("shared", Boolean.TYPE),
    
};

    
/**
     
* readObject is called to restore the state of the StringBuffer from
     
* a stream.
     
*/

    
private synchronized void writeObject(java.io.ObjectOutputStream s)
        
throws java.io.IOException {
        
java.io.ObjectOutputStream.PutField fields = s.putFields();
        
fields.put("value", value);
        
fields.put("count", count);
        
fields.put("shared", false);
        
s.writeFields();
    
}

    
/**
     
* readObject is called to restore the state of the StringBuffer from
     
* a stream.
     
*/

    
private void readObject(java.io.ObjectInputStream s)
        
throws java.io.IOException, ClassNotFoundException {
        
java.io.ObjectInputStream.GetField fields = s.readFields();
        
value = (char[])fields.get("value", null);
        
count = fields.get("count", 0);
    
}
}