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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 }