Source Code of Java - StringBuffer

Bertha 。 2021-09-10 15:54 279阅读 0赞

/* * Copyright (c) 1994, 2008, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. * * * * * * * * * * * * * * * * * * * * */
 
 package java.lang;
 
 
 /** * 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. * * 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. * * The principal operations on a <code>StringBuffer</code> are the * <code>append</code> and <code>insert</code> 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</code> method always adds these characters at the end * of the buffer; the <code>insert</code> method adds the characters at * a specified point. * * For example, if <code>z</code> refers to a string buffer object * whose current contents are "<code>start</code>", then * the method call <code>z.append("le")</code> would cause the string * buffer to contain "<code>startle</code>", whereas * <code>z.insert(4, "le")</code> would alter the string buffer to * contain "<code>starlet</code>". * * In general, if sb refers to an instance of a <code>StringBuffer</code>, * then <code>sb.append(x)</code> has the same effect as * <code>sb.insert(sb.length(), x)</code>. * * 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. * * 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. * * As of release JDK 5, this class has been supplemented with an equivalent * class designed for use by a single thread, {@link StringBuilder}. The * <tt>StringBuilder</tt> 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 { 
 
 /** 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</code> * argument is less than <code>0</code>. */
 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</code> plus the length of the string argument. * * @param str the initial contents of the buffer. * @exception NullPointerException if <code>str</code> is <code>null</code> */
 public StringBuffer(String str) {
 super(str.length() + 16);
 append(str);
 }
 
 /** * Constructs a string buffer that contains the same characters * as the specified <code>CharSequence</code>. The initial capacity of * the string buffer is <code>16</code> plus the length of the * <code>CharSequence</code> argument. * * If the length of the specified <code>CharSequence</code> is * less than or equal to zero, then an empty buffer of capacity * <code>16</code> is returned. * * @param seq the sequence to copy. * @exception NullPointerException if <code>seq</code> is <code>null</code> * @since 1.5 */
 public StringBuffer(CharSequence seq) {
 this(seq.length() + 16);
 append(seq);
 }
 
 public synchronized int length() {
 return count;
 }
 
 public synchronized int capacity() {
 return value.length;
 }
 
 
 public synchronized void ensureCapacity(int minimumCapacity) {
 if (minimumCapacity > value.length) {
 expandCapacity(minimumCapacity);
 }
 }
 
 /** * @since 1.5 */
 public synchronized void trimToSize() {
 super.trimToSize();
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @see #length() */
 public synchronized void setLength(int newLength) {
 super.setLength(newLength);
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @see #length() */
 public synchronized char charAt(int index) {
 if ((index < 0) || (index >= count))
 throw new StringIndexOutOfBoundsException(index);
 return value[index];
 }
 
 /** * @since 1.5 */
 public synchronized int codePointAt(int index) {
 return super.codePointAt(index);
 }
 
 /** * @since 1.5 */
 public synchronized int codePointBefore(int index) {
 return super.codePointBefore(index);
 }
 
 /** * @since 1.5 */
 public synchronized int codePointCount(int beginIndex, int endIndex) {
 return super.codePointCount(beginIndex, endIndex);
 }
 
 /** * @since 1.5 */
 public synchronized int offsetByCodePoints(int index, int codePointOffset) {
 return super.offsetByCodePoints(index, codePointOffset);
 }
 
 /** * @throws NullPointerException {@inheritDoc} * @throws IndexOutOfBoundsException {@inheritDoc} */
 public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
 int dstBegin)
 {
 super.getChars(srcBegin, srcEnd, dst, dstBegin);
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @see #length() */
 public synchronized void setCharAt(int index, char ch) {
 if ((index < 0) || (index >= count))
 throw new StringIndexOutOfBoundsException(index);
 value[index] = ch;
 }
 
 public synchronized StringBuffer append(Object obj) {
 super.append(String.valueOf(obj));
 return this;
 }
 
 public synchronized StringBuffer append(String str) {
 super.append(str);
 return this;
 }
 
 /** * Appends the specified <tt>StringBuffer</tt> to this sequence. * * The characters of the <tt>StringBuffer</tt> argument are appended, * in order, to the contents of this <tt>StringBuffer</tt>, increasing the * length of this <tt>StringBuffer</tt> by the length of the argument. * If <tt>sb</tt> is <tt>null</tt>, then the four characters * <tt>"null"</tt> are appended to this <tt>StringBuffer</tt>. * * Let n be the length of the old character sequence, the one * contained in the <tt>StringBuffer</tt> just prior to execution of the * <tt>append</tt> method. Then the character at index k in * the new character sequence is equal to the character at index k * in the old character sequence, if k is less than n; * otherwise, it is equal to the character at index k-n in the * argument <code>sb</code>. * * This method synchronizes on <code>this</code> (the destination) * object but does not synchronize on the source (<code>sb</code>). * * @param sb the <tt>StringBuffer</tt> to append. * @return a reference to this object. * @since 1.4 */
 public synchronized StringBuffer append(StringBuffer sb) {
 super.append(sb);
 return this;
 }
 
 
 /** * Appends the specified <code>CharSequence</code> to this * sequence. * * The characters of the <code>CharSequence</code> argument are appended, * in order, increasing the length of this sequence by the length of the * argument. * * The result of this method is exactly the same as if it were an * invocation of this.append(s, 0, s.length()); * * This method synchronizes on this (the destination) * object but does not synchronize on the source (<code>s</code>). * * If <code>s</code> is <code>null</code>, then the four characters * <code>"null"</code> are appended. * * @param s the <code>CharSequence</code> to append. * @return a reference to this object. * @since 1.5 */
 public StringBuffer append(CharSequence s) {
 // Note, synchronization achieved via other invocations
 if (s == null)
 s = "null";
 if (s instanceof String)
 return this.append((String)s);
 if (s instanceof StringBuffer)
 return this.append((StringBuffer)s);
 return this.append(s, 0, s.length());
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @since 1.5 */
 public synchronized StringBuffer append(CharSequence s, int start, int end)
 {
 super.append(s, start, end);
 return this;
 }
 
 public synchronized StringBuffer append(char[] str) {
 super.append(str);
 return this;
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} */
 public synchronized StringBuffer append(char[] str, int offset, int len) {
 super.append(str, offset, len);
 return this;
 }
 
 public synchronized StringBuffer append(boolean b) {
 super.append(b);
 return this;
 }
 
 public synchronized StringBuffer append(char c) {
 super.append(c);
 return this;
 }
 
 public synchronized StringBuffer append(int i) {
 super.append(i);
 return this;
 }
 
 /** * @since 1.5 */
 public synchronized StringBuffer appendCodePoint(int codePoint) {
 super.appendCodePoint(codePoint);
 return this;
 }
 
 public synchronized StringBuffer append(long lng) {
 super.append(lng);
 return this;
 }
 
 public synchronized StringBuffer append(float f) {
 super.append(f);
 return this;
 }
 
 public synchronized StringBuffer append(double d) {
 super.append(d);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized StringBuffer delete(int start, int end) {
 super.delete(start, end);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized StringBuffer deleteCharAt(int index) {
 super.deleteCharAt(index);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized StringBuffer replace(int start, int end, String str) {
 super.replace(start, end, str);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized String substring(int start) {
 return substring(start, count);
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @since 1.4 */
 public synchronized CharSequence subSequence(int start, int end) {
 return super.substring(start, end);
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized String substring(int start, int end) {
 return super.substring(start, end);
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} * @since 1.2 */
 public synchronized StringBuffer insert(int index, char[] str, int offset,
 int len)
 {
 super.insert(index, str, offset, len);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public synchronized StringBuffer insert(int offset, Object obj) {
 super.insert(offset, String.valueOf(obj));
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public synchronized StringBuffer insert(int offset, String str) {
 super.insert(offset, str);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public synchronized StringBuffer insert(int offset, char[] str) {
 super.insert(offset, str);
 return this;
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @since 1.5 */
 public StringBuffer insert(int dstOffset, CharSequence s) {
 // Note, synchronization achieved via other invocations
 if (s == null)
 s = "null";
 if (s instanceof String)
 return this.insert(dstOffset, (String)s);
 return this.insert(dstOffset, s, 0, s.length());
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} * @since 1.5 */
 public synchronized StringBuffer insert(int dstOffset, CharSequence s,
 int start, int end)
 {
 super.insert(dstOffset, s, start, end);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public StringBuffer insert(int offset, boolean b) {
 return insert(offset, String.valueOf(b));
 }
 
 /** * @throws IndexOutOfBoundsException {@inheritDoc} */
 public synchronized StringBuffer insert(int offset, char c) {
 super.insert(offset, c);
 return this;
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public StringBuffer insert(int offset, int i) {
 return insert(offset, String.valueOf(i));
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public StringBuffer insert(int offset, long l) {
 return insert(offset, String.valueOf(l));
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public StringBuffer insert(int offset, float f) {
 return insert(offset, String.valueOf(f));
 }
 
 /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */
 public StringBuffer insert(int offset, double d) {
 return insert(offset, String.valueOf(d));
 }
 
 /** * @throws NullPointerException {@inheritDoc} * @since 1.4 */
 public int indexOf(String str) {
 return indexOf(str, 0);
 }
 
 /** * @throws NullPointerException {@inheritDoc} * @since 1.4 */
 public synchronized int indexOf(String str, int fromIndex) {
 return String.indexOf(value, 0, count,
 str.toCharArray(), 0, str.length(), fromIndex);
 }
 
 /** * @throws NullPointerException {@inheritDoc} * @since 1.4 */
 public int lastIndexOf(String str) {
 // Note, synchronization achieved via other invocations
 return lastIndexOf(str, count);
 }
 
 /** * @throws NullPointerException {@inheritDoc} * @since 1.4 */
 public synchronized int lastIndexOf(String str, int fromIndex) {
 return String.lastIndexOf(value, 0, count,
 str.toCharArray(), 0, str.length(), fromIndex);
 }
 
 /** * @since JDK1.0.2 */
 public synchronized StringBuffer reverse() {
 super.reverse();
 return this;
 }
 
 public synchronized String toString() {
 return new String(value, 0, count);
 }
 
 /** * 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);
 }
 }

来源：[http://blog.csdn.net/f562867448/article/details/8684506][http_blog.csdn.net_f562867448_article_details_8684506]

[http_blog.csdn.net_f562867448_article_details_8684506]: http://blog.csdn.net/f562867448/article/details/8684506