Scala example source code file (AbstractPromise.java)

This example Scala source code file (AbstractPromise.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

abstractpromise, atomicreferencefieldupdater, concurrent, exceptionininitializererror, object, throwable, utilities

The AbstractPromise.java Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.concurrent.impl;


import scala.concurrent.util.Unsafe;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;



abstract class AbstractPromise {
    private volatile Object _ref;

    final static long _refoffset;

    static {
	try {
	    _refoffset = Unsafe.instance.objectFieldOffset(AbstractPromise.class.getDeclaredField("_ref"));
	} catch (Throwable t) {
	    throw new ExceptionInInitializerError(t);
	}
    }

    protected final boolean updateState(Object oldState, Object newState) {
	return Unsafe.instance.compareAndSwapObject(this, _refoffset, oldState, newState);
    }

    protected final Object getState() {
	return _ref;
    }

    protected final static AtomicReferenceFieldUpdater<AbstractPromise, Object> updater =
	AtomicReferenceFieldUpdater.newUpdater(AbstractPromise.class, Object.class, "_ref");
}