1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util;
27
28 /**
29 * This exception may be thrown by methods that have detected concurrent
30 * modification of an object when such modification is not permissible.
31 * <p>
32 * For example, it is not generally permissible for one thread to modify a Collection
33 * while another thread is iterating over it. In general, the results of the
34 * iteration are undefined under these circumstances. Some Iterator
35 * implementations (including those of all the general purpose collection implementations
36 * provided by the JRE) may choose to throw this exception if this behavior is
37 * detected. Iterators that do this are known as <i>fail-fast</i> iterators,
38 * as they fail quickly and cleanly, rather that risking arbitrary,
39 * non-deterministic behavior at an undetermined time in the future.
40 * <p>
41 * Note that this exception does not always indicate that an object has
42 * been concurrently modified by a <i>different</i> thread. If a single
43 * thread issues a sequence of method invocations that violates the
44 * contract of an object, the object may throw this exception. For
45 * example, if a thread modifies a collection directly while it is
46 * iterating over the collection with a fail-fast iterator, the iterator
47 * will throw this exception.
48 *
49 * <p>Note that fail-fast behavior cannot be guaranteed as it is, generally
50 * speaking, impossible to make any hard guarantees in the presence of
51 * unsynchronized concurrent modification. Fail-fast operations
52 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
53 * Therefore, it would be wrong to write a program that depended on this
54 * exception for its correctness: <i><tt>ConcurrentModificationException</tt>
55 * should be used only to detect bugs.</i>
56 *
57 * @author Josh Bloch
58 * @see Collection
59 * @see Iterator
60 * @see ListIterator
61 * @see Vector
62 * @see LinkedList
63 * @see HashSet
64 * @see Hashtable
65 * @see TreeMap
66 * @see AbstractList
67 * @since 1.2
68 */
69 public class ConcurrentModificationException extends RuntimeException {
70 /**
71 * Constructs a ConcurrentModificationException with no
72 * detail message.
73 */
74 public ConcurrentModificationException() {
75 }
76
77 /**
78 * Constructs a <tt>ConcurrentModificationException</tt> with the
79 * specified detail message.
80 *
81 * @param message the detail message pertaining to this exception.
82 */
83 public ConcurrentModificationException(String message) {
84 super(message);
85 }
86 }
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