Class ConcurrentModificationException

All Implemented Interfaces:

public class ConcurrentModificationException
extends RuntimeException

Untamed: 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 permssible 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 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 thow 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.

1.14, 12/03/01
Josh Bloch
See Also:
Collection, Iterator, ListIterator, Vector, LinkedList, HashSet, Hashtable, TreeMap, AbstractList, Serialized Form

Field Summary
Fields inherited from class java.lang.RuntimeException
Fields inherited from class java.lang.Throwable
Constructor Summary
          Enabled: Constructs a ConcurrentModificationException with no detail message.
ConcurrentModificationException(String message)
          Enabled: Constructs a ConcurrentModificationException with the specified detail message.
Methods inherited from class java.lang.Throwable
backtrace, eStack, fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, javaStack, leaf, printStackTrace, printStackTrace, printStackTrace, printThrowableOn, setStackTrace, toString, unwrap
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail


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


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

message - the detail message pertaining to this exception.