util
Class SinglePermitMap

java.lang.Object
  |
  +--util.SinglePermitMap

public class SinglePermitMap

extends Object

A map class that allows for multiple threads access to objects but maintains that one thread will have access at a time. Threads that request an object that is currently being used will block until the object permit has been released.

Version:

$Revision: 1.5 $

Author:

David Jurgens

Field Summary

private static Boolean	AVAILABLE
private Map	lockedObjects Map containing the set of keys and values.
private static Boolean	NOT_AVAILABLE
private Map	permitStatus Map containing information regarding whether an object is currently released on permit.
private Map	waitQueues Map containing ordered wait queues for threads requesting an object.

Constructor Summary

SinglePermitMap()

Method Summary

Object	acquire(Object key) Returns the the value if no other Thread currently has it, or blocks until the access is allowed.
Object	acquireNonBlocking(Object key) Returns the the value if no other Thread currently has it, or if the object is currently locked, returns null immediately rather than waiting for the value to be released.
boolean	isEmpty()
Set	keySet()
Object	put(Object key, Object value)
void	release(Object key)
int	size()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

AVAILABLE

private static final Boolean AVAILABLE

NOT_AVAILABLE

private static final Boolean NOT_AVAILABLE

lockedObjects

private final Map lockedObjects

Map containing the set of keys and values.

permitStatus

private final Map permitStatus

Map containing information regarding whether an object is currently released on permit.

waitQueues

private final Map waitQueues

Map containing ordered wait queues for threads requesting an object.

Constructor Detail

SinglePermitMap

public SinglePermitMap()

Method Detail

acquire

public Object acquire(Object key)

Returns the the value if no other Thread currently has it, or blocks until the access is allowed. Blocking threads are notified in order of call. If the value has not been put into the map, null is immediately returned.

acquireNonBlocking

public Object acquireNonBlocking(Object key)

Returns the the value if no other Thread currently has it, or if the object is currently locked, returns null immediately rather than waiting for the value to be released.

isEmpty

public boolean isEmpty()

keySet

public Set keySet()

put

public Object put(Object key,
                  Object value)

release

public void release(Object key)

size

public int size()