/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

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 NegativeArraySizeException if 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 str the 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);
 }

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

 /**
 * @since 1.5
 */
 @Override
 public synchronized int codePointCount(int beginIndex, int endIndex) {
 return super.codePointCount(beginIndex, endIndex);
 }

 /**
 * @since 1.5
 */
 @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 sb the {@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);
 }
}