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    1   /*
    2    * Copyright (c) 1997, 2010, 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     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       private static final long serialVersionUID = -3666751008965953603L;
   71   
   72       /**
   73        * Constructs a ConcurrentModificationException with no
   74        * detail message.
   75        */
   76       public ConcurrentModificationException() {
   77       }
   78   
   79       /**
   80        * Constructs a {@code ConcurrentModificationException} with the
   81        * specified detail message.
   82        *
   83        * @param message the detail message pertaining to this exception.
   84        */
   85       public ConcurrentModificationException(String message) {
   86           super(message);
   87       }
   88   
   89       /**
   90        * Constructs a new exception with the specified cause and a detail
   91        * message of {@code (cause==null ? null : cause.toString())} (which
   92        * typically contains the class and detail message of {@code cause}.
   93        *
   94        * @param  cause the cause (which is saved for later retrieval by the
   95        *         {@link Throwable#getCause()} method).  (A {@code null} value is
   96        *         permitted, and indicates that the cause is nonexistent or
   97        *         unknown.)
   98        * @since  1.7
   99        */
  100       public ConcurrentModificationException(Throwable cause) {
  101           super(cause);
  102       }
  103   
  104       /**
  105        * Constructs a new exception with the specified detail message and
  106        * cause.
  107        *
  108        * <p>Note that the detail message associated with <code>cause</code> is
  109        * <i>not</i> automatically incorporated in this exception's detail
  110        * message.
  111        *
  112        * @param  message the detail message (which is saved for later retrieval
  113        *         by the {@link Throwable#getMessage()} method).
  114        * @param  cause the cause (which is saved for later retrieval by the
  115        *         {@link Throwable#getCause()} method).  (A {@code null} value
  116        *         is permitted, and indicates that the cause is nonexistent or
  117        *         unknown.)
  118        * @since 1.7
  119        */
  120       public ConcurrentModificationException(String message, Throwable cause) {
  121           super(message, cause);
  122       }
  123   }

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