1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * 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 {@code ConcurrentModificationException} 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>{@code ConcurrentModificationException}
55 * should be used only to detect bugs.</i>
56 *
57 * @author Josh Bloch
58 * @see Collection
59 * @see Iterator
60 * @see Spliterator
61 * @see ListIterator
62 * @see Vector
63 * @see LinkedList
64 * @see HashSet
65 * @see Hashtable
66 * @see TreeMap
67 * @see AbstractList
68 * @since 1.2
69 */
70 public class ConcurrentModificationException extends RuntimeException {
71 private static final long serialVersionUID = -3666751008965953603L;
72
73 /**
74 * Constructs a ConcurrentModificationException with no
75 * detail message.
76 */
77 public ConcurrentModificationException() {
78 }
79
80 /**
81 * Constructs a {@code ConcurrentModificationException} with the
82 * specified detail message.
83 *
84 * @param message the detail message pertaining to this exception.
85 */
86 public ConcurrentModificationException(String message) {
87 super(message);
88 }
89
90 /**
91 * Constructs a new exception with the specified cause and a detail
92 * message of {@code (cause==null ? null : cause.toString())} (which
93 * typically contains the class and detail message of {@code cause}.
94 *
95 * @param cause the cause (which is saved for later retrieval by the
96 * {@link Throwable#getCause()} method). (A {@code null} value is
97 * permitted, and indicates that the cause is nonexistent or
98 * unknown.)
99 * @since 1.7
100 */
101 public ConcurrentModificationException(Throwable cause) {
102 super(cause);
103 }
104
105 /**
106 * Constructs a new exception with the specified detail message and
107 * cause.
108 *
109 * <p>Note that the detail message associated with <code>cause</code> is
110 * <i>not</i> automatically incorporated in this exception's detail
111 * message.
112 *
113 * @param message the detail message (which is saved for later retrieval
114 * by the {@link Throwable#getMessage()} method).
115 * @param cause the cause (which is saved for later retrieval by the
116 * {@link Throwable#getCause()} method). (A {@code null} value
117 * is permitted, and indicates that the cause is nonexistent or
118 * unknown.)
119 * @since 1.7
120 */
121 public ConcurrentModificationException(String message, Throwable cause) {
122 super(message, cause);
123 }
124 }