Mercurial > hg > icedtea9-forest > jdk
changeset 5774:9e15068b6946
7100996: (spec str) IndexOutOfBoundsException when using a StringBuffer from multiple threads
Summary: add usage note to clarify thread safety
Reviewed-by: briangoetz, mduigou
Contributed-by: jim.gish@oracle.com
author | jgish |
---|---|
date | Fri, 29 Jun 2012 15:36:14 -0700 |
parents | 819258b5002e |
children | 9df29b658145 |
files | src/share/classes/java/lang/StringBuffer.java |
diffstat | 1 files changed, 44 insertions(+), 35 deletions(-) [+] |
line wrap: on
line diff
--- a/src/share/classes/java/lang/StringBuffer.java Thu Jun 28 22:44:21 2012 -0700 +++ b/src/share/classes/java/lang/StringBuffer.java Fri Jun 29 15:36:14 2012 -0700 @@ -1,5 +1,5 @@ /* - * Copyright (c) 1994, 2008, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 1994, 2012, 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 @@ -39,29 +39,38 @@ * 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</code> are the - * <code>append</code> and <code>insert</code> methods, which are + * 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</code> method always adds these characters at the end - * of the buffer; the <code>insert</code> method adds the characters at + * {@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</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>". + * 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</code>, - * then <code>sb.append(x)</code> has the same effect as - * <code>sb.insert(sb.length(), x)</code>. + * 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 + * 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 @@ -101,8 +110,8 @@ * the specified initial capacity. * * @param capacity the initial capacity. - * @exception NegativeArraySizeException if the <code>capacity</code> - * argument is less than <code>0</code>. + * @exception NegativeArraySizeException if the {@code capacity} + * argument is less than {@code 0}. */ public StringBuffer(int capacity) { super(capacity); @@ -111,10 +120,10 @@ /** * 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. + * {@code 16} 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> + * @exception NullPointerException if {@code str} is {@code null} */ public StringBuffer(String str) { super(str.length() + 16); @@ -123,16 +132,16 @@ /** * 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. + * 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</code> is + * If the length of the specified {@code CharSequence} is * less than or equal to zero, then an empty buffer of capacity - * <code>16</code> is returned. + * {@code 16} is returned. * * @param seq the sequence to copy. - * @exception NullPointerException if <code>seq</code> is <code>null</code> + * @exception NullPointerException if {@code seq} is {@code null} * @since 1.5 */ public StringBuffer(CharSequence seq) { @@ -253,10 +262,10 @@ * 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</code>. + * argument {@code sb}. * <p> - * This method synchronizes on <code>this</code> (the destination) - * object but does not synchronize on the source (<code>sb</code>). + * This method synchronizes on {@code this}, the destination + * object, but does not synchronize on the source ({@code sb}). * * @param sb the <tt>StringBuffer</tt> to append. * @return a reference to this object. @@ -269,23 +278,23 @@ /** - * Appends the specified <code>CharSequence</code> to this + * Appends the specified {@code CharSequence} to this * sequence. * <p> - * The characters of the <code>CharSequence</code> argument are appended, + * 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 this (the destination) - * object but does not synchronize on the source (<code>s</code>). + * <p>This method synchronizes on {@code this}, the destination + * object, but does not synchronize on the source ({@code s}). * - * <p>If <code>s</code> is <code>null</code>, then the four characters - * <code>"null"</code> are appended. + * <p>If {@code s} is {@code null}, then the four characters + * {@code "null"} are appended. * - * @param s the <code>CharSequence</code> to append. + * @param s the {@code CharSequence} to append. * @return a reference to this object. * @since 1.5 */