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Internal package of Alachisoft.
There is a newer version: 5.3.3
package Alachisoft.NCache.Common.Threading;

/**
 * The caller may choose to check for the result at a later time, or immediately and it may block or not. Both the caller and responder have to know the promise.
 * 
 * 

 * Allows a thread to submit an asynchronous request and to wait for the result. 
Author: Chris Koiak, Bela Ban
 Date: 12/03/2003
 */
public class Promise {

    /**
     * The result of the request
     */
    private Object _result = null;
    /**
     * Used to wait on the result
     */
    private Object _mutex = new Object();

    /**
     * If result was already submitted, returns it immediately, else blocks until results becomes available.      *
     *
     * @param timeout Maximum time to wait for result.
     * @return Promise result
     */
    public final Object WaitResult(long timeout) {
        Object ret = null;

        synchronized (_mutex) {
            if (_result != null) {
                ret = _result;
                _result = null;
                return ret;
            }
            if (timeout <= 0) {
                try {
                    Monitor.wait(_mutex); //_mutex.wait();
                } catch (java.lang.InterruptedException ex) {
                    //Basit: Should use NCacheLogs
                    //Trace.error("Promise.WaitResult", "exception=" + ex.toString());
                }
            } else {
                try {
                    Monitor.wait(_mutex, timeout);// _mutex.wait(timeout);
                } catch (java.lang.InterruptedException ex) {
                    //Basit: Should use NCacheLogs
                    //Trace.error("Promise.WaitResult:", "exception=" + ex.toString());
                }
            }

            // SAL: Cosider Trace
            if (_result != null) {
                ret = _result;
                _result = null;
                return ret;
            }
            return null;
        }
    }

    /**
     * Checks whether result is available. Does not block.
     *
     * @return Result if available
     */
    public final Object getIsResultAvailable() {
        synchronized (_mutex) {
            return _result;
        }
    }

    /**
     * Sets the result and notifies any threads waiting for it
     *
     * @param obj Result of request
     */
    public final void SetResult(Object obj) {
        synchronized (_mutex) {
            _result = obj;
            Monitor.pulse(_mutex); //_mutex.notifyAll();
        }
    }

    /**
     * Clears the result and causes all waiting threads to return
     */
    public final void Reset() {
        synchronized (_mutex) {
            _result = null;
            Monitor.pulse(_mutex);//_mutex.notifyAll();
        }
    }

    /**
     * String representation of the result
     *
     * @return String representation of the result
     */
    @Override
    public String toString() {
        return "result=" + _result;
    }
}