ConcurrentModificationException.java revision 4c89023ef86f29fa9add7db2574f2169fe842577 
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25
26package 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 */
70public 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}
125