EDU.oswego.cs.dl.util.concurrent

Class SynchronizedRef

Implemented Interfaces:
Executor
Known Direct 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 Object
value_
The maintained reference *

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

lock_

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

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

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

execute, getLock

Field Details

value_

protected Object value_
The maintained reference *

Constructor Details

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 Details

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