EDU.oswego.cs.dl.util.concurrent
Class SynchronizedRef

java.lang.Object
  EDU.oswego.cs.dl.util.concurrent.SynchronizedVariable
      EDU.oswego.cs.dl.util.concurrent.SynchronizedRef

All Implemented Interfaces:

Executor

Direct Known Subclasses:

WaitableRef

public class SynchronizedRef
extends SynchronizedVariable

A simple class maintaining a single reference variable that is always accessed and updated under synchronization.

[ Introduction to this package. ]

Field Summary

protected java.lang.Object

value_ The maintained reference

Fields inherited from class EDU.oswego.cs.dl.util.concurrent.SynchronizedVariable

lock_

Constructor Summary

SynchronizedRef(java.lang.Object initialValue)
Create a SynchronizedRef initially holding the given reference and using its own internal lock.

SynchronizedRef(java.lang.Object initialValue, java.lang.Object lock)
Make a new SynchronizedRef with the given initial value, and using the supplied lock.

Method Summary

boolean	commit(java.lang.Object assumedValue, java.lang.Object newValue) Set value to newValue only if it is currently assumedValue.
java.lang.Object	get() Return the current value
java.lang.Object	set(java.lang.Object newValue) Set to newValue.
java.lang.Object	swap(SynchronizedRef other) Atomically swap values with another SynchronizedRef.

Methods inherited from class EDU.oswego.cs.dl.util.concurrent.SynchronizedVariable

execute, getLock

Methods inherited from class java.lang.Object

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

Field Detail

value_

protected java.lang.Object value_

The maintained reference

Constructor Detail

SynchronizedRef

public SynchronizedRef(java.lang.Object initialValue)

Create a SynchronizedRef initially holding the given reference and using its own internal lock.

SynchronizedRef

public SynchronizedRef(java.lang.Object initialValue,
                       java.lang.Object lock)

Make a new SynchronizedRef with the given initial value, and using the supplied lock.

Method Detail

get

public final java.lang.Object get()

Return the current value

set

public java.lang.Object set(java.lang.Object newValue)

Set to newValue.

Returns:

the old value

commit

public boolean commit(java.lang.Object assumedValue,
                      java.lang.Object newValue)

Set value to newValue only if it is currently assumedValue.

Returns:

true if successful

swap

public java.lang.Object swap(SynchronizedRef other)

Atomically swap values with another SynchronizedRef. Uses identityHashCode to avoid deadlock when two SynchronizedRefs attempt to simultaneously swap with each other. (Note: Ordering via identyHashCode is not strictly guaranteed by the language specification to return unique, orderable values, but in practice JVMs rely on them being unique.)

Returns:

the new value