EDU.oswego.cs.dl.util.concurrent

Class SynchronizedRef

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 Objectvalue_
The maintained reference *
Constructor Summary
SynchronizedRef(Object initialValue)
Create a SynchronizedRef initially holding the given reference and using its own internal lock.
SynchronizedRef(Object initialValue, Object lock)
Make a new SynchronizedRef with the given initial value, and using the supplied lock.
Method Summary
booleancommit(Object assumedValue, Object newValue)
Set value to newValue only if it is currently assumedValue.
Objectget()
Return the current value
Objectset(Object newValue)
Set to newValue.
Objectswap(SynchronizedRef other)
Atomically swap values with another SynchronizedRef.

Field Detail

value_

protected Object value_
The maintained reference *

Constructor Detail

SynchronizedRef

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

SynchronizedRef

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

Method Detail

commit

public boolean commit(Object assumedValue, Object newValue)
Set value to newValue only if it is currently assumedValue.

Returns: true if successful

get

public final Object get()
Return the current value

set

public Object set(Object newValue)
Set to newValue.

Returns: the old value

swap

public 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