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Java > Open Source Codes > java > util > ConcurrentModificationException


1 /*
2  * @(#)ConcurrentModificationException.java 1.18 04/06/22
3  *
4  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6  */
7
8 package java.util;
9
10 /**
11  * This exception may be thrown by methods that have detected concurrent
12  * modification of an object when such modification is not permissible.
13  * <p>
14  * For example, it is not generally permissible for one thread to modify a Collection
15  * while another thread is iterating over it. In general, the results of the
16  * iteration are undefined under these circumstances. Some Iterator
17  * implementations (including those of all the general purpose collection implementations
18  * provided by the JRE) may choose to throw this exception if this behavior is
19  * detected. Iterators that do this are known as <i>fail-fast</i> iterators,
20  * as they fail quickly and cleanly, rather that risking arbitrary,
21  * non-deterministic behavior at an undetermined time in the future.
22  * <p>
23  * Note that this exception does not always indicate that an object has
24  * been concurrently modified by a <i>different</i> thread. If a single
25  * thread issues a sequence of method invocations that violates the
26  * contract of an object, the object may throw this exception. For
27  * example, if a thread modifies a collection directly while it is
28  * iterating over the collection with a fail-fast iterator, the iterator
29  * will throw this exception.
30  *
31  * <p>Note that fail-fast behavior cannot be guaranteed as it is, generally
32  * speaking, impossible to make any hard guarantees in the presence of
33  * unsynchronized concurrent modification. Fail-fast operations
34  * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
35  * Therefore, it would be wrong to write a program that depended on this
36  * exception for its correctness: <i><tt>ConcurrentModificationException</tt>
37  * should be used only to detect bugs.</i>
38  *
39  * @author Josh Bloch
40  * @version 1.18, 06/22/04
41  * @see Collection
42  * @see Iterator
43  * @see ListIterator
44  * @see Vector
45  * @see LinkedList
46  * @see HashSet
47  * @see Hashtable
48  * @see TreeMap
49  * @see AbstractList
50  * @since 1.2
51  */
52 public class ConcurrentModificationException extends RuntimeException JavaDoc {
53     /**
54      * Constructs a ConcurrentModificationException with no
55      * detail message.
56      */
57     public ConcurrentModificationException() {
58     }
59
60     /**
61      * Constructs a <tt>ConcurrentModificationException</tt> with the
62      * specified detail message.
63      *
64      * @param message the detail message pertaining to this exception.
65      */
66     public ConcurrentModificationException(String JavaDoc message) {
67     super(message);
68     }
69 }
70
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