Java™ Platform
Standard Ed. 6

java.util
Class ConcurrentModificationException

java.lang.Object
  extended by java.lang.Throwable
      extended by java.lang.Exception
          extended by java.lang.RuntimeException
              extended by java.util.ConcurrentModificationException
All Implemented Interfaces:
Serializable

public class ConcurrentModificationException
extends RuntimeException

This exception may be thrown by methods that have detected concurrent modification of an object when such modification is not permissible.

For example, it is not generally permissible for one thread to modify a Collection while another thread is iterating over it. In general, the results of the iteration are undefined under these circumstances. Some Iterator implementations (including those of all the general purpose collection implementations provided by the JRE) may choose to throw this exception if this behavior is detected. Iterators that do this are known as fail-fast iterators, as they fail quickly and cleanly, rather that risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that this exception does not always indicate that an object has been concurrently modified by a different thread. If a single thread issues a sequence of method invocations that violates the contract of an object, the object may throw this exception. For example, if a thread modifies a collection directly while it is iterating over the collection with a fail-fast iterator, the iterator will throw this exception.

Note that fail-fast behavior cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast operations throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: ConcurrentModificationException should be used only to detect bugs.

Since:
1.2
See Also:
Collection, Iterator, ListIterator, Vector, LinkedList, HashSet, Hashtable, TreeMap, AbstractList, Serialized Form

Constructor Summary
ConcurrentModificationException()
          Constructs a ConcurrentModificationException with no detail message.
ConcurrentModificationException(String message)
          Constructs a ConcurrentModificationException with the specified detail message.
 
Method Summary
 
Methods inherited from class java.lang.Throwable
fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

ConcurrentModificationException

public ConcurrentModificationException()
Constructs a ConcurrentModificationException with no detail message.


ConcurrentModificationException

public ConcurrentModificationException(String message)
Constructs a ConcurrentModificationException with the specified detail message.

Parameters:
message - the detail message pertaining to this exception.

Java™ Platform
Standard Ed. 6

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