de.aristaflow.adept2.util.threading

Class ResultExchange<T>

java.lang.Object

de.aristaflow.adept2.util.threading.ResultExchange<T>

Type Parameters:

T - The type of the result.

All Implemented Interfaces:

java.util.concurrent.Future<T>

public class ResultExchange<T>
extends java.lang.Object
implements java.util.concurrent.Future<T>

This class provides the means to exchange a result between different threads. It resembles a Future except for the possibility to cancel it.
The implementation is based on a CountDownLatch. This is awaited by the result readers and signalled by the writer.

When using it make sure to call endComputation(Object) or failComputation(Throwable) under all circumstances after making the instance of ResultExchange available to other threads, e. g.:

 ResultExchange re;
 Throwable t = new Throwable("Computation failed due to unknown reasons");
 try
 {
   ...
   re.endComputation(...);
   t = null;
 }
 catch (Exception e)
 {
   ...
   t = e;
 }
 finally
 {
   re.failComputation(t);
 }
 

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	done Whether the result has been computed (or failed to compute).
protected java.util.concurrent.CountDownLatch	latch The latch for signalling the result being available.
protected T	result The result after computation.
protected java.lang.Throwable	throwable The throwable which caused the computation to fail.

Constructor Summary

Constructors

Constructor and Description
ResultExchange() Creates a new result exchange.

Method Summary

Modifier and Type	Method and Description
boolean	cancel(boolean mayInterruptIfRunning)
void	endComputation(T res) Computation has ended with the designated result to be provided by this ResultExchange.
void	failComputation(java.lang.Throwable t) Computation has failed with the designated throwable to be provided by this ResultExchange unless the designated throwable is null.
T	get()
T	get(long timeout, java.util.concurrent.TimeUnit unit)
boolean	isCancelled()
boolean	isDone()

Methods inherited from class java.lang.Object

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

Field Detail

latch

protected final java.util.concurrent.CountDownLatch latch

The latch for signalling the result being available.

done

protected volatile boolean done

Whether the result has been computed (or failed to compute).

result

protected T result

The result after computation.

throwable

protected java.lang.Throwable throwable

The throwable which caused the computation to fail.

Constructor Detail

ResultExchange

public ResultExchange()

Creates a new result exchange.

Method Detail

endComputation

public void endComputation(T res)

Computation has ended with the designated result to be provided by this ResultExchange.

Parameters:

res - The result to be provided by this ResultExchange

failComputation

public void failComputation(java.lang.Throwable t)

Computation has failed with the designated throwable to be provided by this ResultExchange unless the designated throwable is null. This helps signalling the computation within a finally.

Parameters:

t - The throwable to be provided instead of a result by this ResultExchange. Use null to indicate no failure.

cancel

public boolean cancel(boolean mayInterruptIfRunning)

Specified by:

cancel in interface java.util.concurrent.Future<T>

isCancelled

public boolean isCancelled()

Specified by:

isCancelled in interface java.util.concurrent.Future<T>

isDone

public boolean isDone()

Specified by:

isDone in interface java.util.concurrent.Future<T>

get

public T get()
      throws java.lang.InterruptedException,
             java.util.concurrent.ExecutionException

Specified by:

get in interface java.util.concurrent.Future<T>

Throws:

java.lang.InterruptedException

java.util.concurrent.ExecutionException

get

public T get(long timeout,
             java.util.concurrent.TimeUnit unit)
      throws java.lang.InterruptedException,
             java.util.concurrent.ExecutionException,
             java.util.concurrent.TimeoutException

Specified by:

get in interface java.util.concurrent.Future<T>

Throws:

java.lang.InterruptedException

java.util.concurrent.ExecutionException

java.util.concurrent.TimeoutException