java.util.concurrent

Class FutureTask<V>

Implemented Interfaces:
Future<V>, Runnable

public class FutureTask<V>
extends Object
implements Future<V>, Runnable

A cancellable asynchronous computation. This class provides a base implementation of Future, with methods to start and cancel a computation, query to see if the computation is complete, and retrieve the result of the computation. The result can only be retrieved when the computation has completed; the get method will block if the computation has not yet completed. Once the computation has completed, the computation cannot be restarted or cancelled.

A FutureTask can be used to wrap a Callable or Runnable object. Because FutureTask implements Runnable, a FutureTask can be submitted to an Executor for execution.

In addition to serving as a standalone class, this class provides protected functionality that may be useful when creating customized task classes.

Since:
1.5

Constructor Summary

FutureTask(Callable callable)
Creates a FutureTask that will upon running, execute the given Callable.
FutureTask(Runnable runnable, V result)
Creates a FutureTask that will upon running, execute the given Runnable, and arrange that get will return the given result on successful completion.

Method Summary

boolean
cancel(boolean mayInterruptIfRunning)
protected void
done()
Protected method invoked when this task transitions to state isDone (whether normally or via cancellation).
V
get()
V
get(long timeout, TimeUnit unit)
boolean
isCancelled()
boolean
isDone()
void
run()
Sets this Future to the result of computation unless it has been cancelled.
protected boolean
runAndReset()
Executes the computation without setting its result, and then resets this Future to initial state, failing to do so if the computation encounters an exception or is cancelled.
protected void
set(V v)
Sets the result of this Future to the given value unless this future has already been set or has been cancelled.
protected void
setException(Throwable t)
Causes this future to report an ExecutionException with the given throwable as its cause, unless this Future has already been set or has been cancelled.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

FutureTask

public FutureTask(Callable callable)
Creates a FutureTask that will upon running, execute the given Callable.
Parameters:
callable - the callable task
Throws:
NullPointerException - if callable is null

FutureTask

public FutureTask(Runnable runnable,
                  V result)
Creates a FutureTask that will upon running, execute the given Runnable, and arrange that get will return the given result on successful completion.
Parameters:
runnable - the runnable task
result - the result to return on successful completion. If you don't need a particular result, consider using constructions of the form: Future<?> f = new FutureTask<Object>(runnable, null)
Throws:
NullPointerException - if runnable is null
Usages and Demos :

View More Examples of FutureTask(Runnable runnable,V result)
   1:     public void invokeAneWait(Runnable r) throws InterruptedException, ExecutionException {
   2:         FutureTask task = new FutureTask(r, null);
   3:         tpe.execute(task);
   4:         task.get();
   5:     }

View Full Code Here
   1:         for (int i = 0; i < numThreads; i++) {
   2:             t[i] = new FutureTask(this, null);
   3:             threadpool.execute(t[i]);
   4:         }
   5:         for (int i = 0; i < numThreads; i++) {

View Full Code Here

Method Details

cancel

public boolean cancel(boolean mayInterruptIfRunning)
Specified by:
cancel in interface Future<V>

done

protected void done()
Protected method invoked when this task transitions to state isDone (whether normally or via cancellation). The default implementation does nothing. Subclasses may override this method to invoke completion callbacks or perform bookkeeping. Note that you can query status inside the implementation of this method to determine whether this task has been cancelled.

get

public V get()
            throws InterruptedException,
                   ExecutionException
Specified by:
get in interface Future<V>
Usages and Demos :

View More Examples of get()
   1:     public void invokeAneWait(Runnable r) throws InterruptedException, ExecutionException {
   2:         FutureTask task = new FutureTask(r, null);
   3:         tpe.execute(task);
   4:         ...
   5:         task.get();
   6:     }
   7: 
   8:     public void shutdown() {

View Full Code Here
   1: import java.util.concurrent.Future;
   2: import java.util.concurrent.FutureTask;
   3: import java.util.concurrent.TimeUnit;
   4:         ...
   5:     {
   6:         private static class FutureNode extends FutureTask
   7:         {
   8:         ...
   9: 
  10:         private final FutureTask future;
  11: 
  12:         ...
  13:         {
  14:             return future.get();

View Full Code Here
   1: 
   2: import edu.emory.mathcs.backport.java.util.concurrent.FutureTask;
   3: import edu.emory.mathcs.backport.java.util.concurrent.ScheduledThreadPoolExecutor;
   4:         ...
   5:     public Message request(Destination destination, Message message, long timeout) throws JMSException {
   6:         FutureTask future = null;
   7:         String correlationID = message.getJMSCorrelationID();
   8:         ...
   9:             if (timeout < 0) {
  10:                 return (Message) future.get();
  11:             }

View Full Code Here
   1: import edu.emory.mathcs.backport.java.util.concurrent.ExecutionException;
   2: import edu.emory.mathcs.backport.java.util.concurrent.FutureTask;
   3: import edu.emory.mathcs.backport.java.util.concurrent.LinkedBlockingQueue;
   4:         ...
   5:                 try {
   6:                     final FutureTask result = new FutureTask(new Callable() {
   7:                         public Object call() throws Exception {
   8:         ...
   9:                     executor.execute(result);
  10:                     Location location = (Location) result.get();
  11:                     appendLogFileId = location.getLogFileId();
  12:         ...
  13:             executor.execute(result);
  14:             return (Location) result.get();

View Full Code Here

get

public V get(long timeout,
             TimeUnit unit)
            throws InterruptedException,
                   ExecutionException,
                   TimeoutException
Specified by:
get in interface Future<V>
Usages and Demos :

View More Examples of get(long timeout,TimeUnit unit)
   1: import java.util.concurrent.Future;
   2: import java.util.concurrent.FutureTask;
   3: import java.util.concurrent.TimeUnit;
   4:         ...
   5:     {
   6:         private static class FutureNode extends FutureTask
   7:         {
   8:         ...
   9: 
  10:         private final FutureTask future;
  11: 
  12:         ...
  13:         {
  14:             return future.get(timeout, unit);

View Full Code Here
   1: 
   2: import edu.emory.mathcs.backport.java.util.concurrent.FutureTask;
   3: import edu.emory.mathcs.backport.java.util.concurrent.ScheduledThreadPoolExecutor;
   4:         ...
   5:     public Message request(Destination destination, Message message, long timeout) throws JMSException {
   6:         FutureTask future = null;
   7:         String correlationID = message.getJMSCorrelationID();
   8:         ...
   9:             else {
  10:                 return (Message) future.get(timeout, TimeUnit.MILLISECONDS);
  11:             }

View Full Code Here

isCancelled

public boolean isCancelled()
Specified by:
isCancelled in interface Future<V>
Usages and Demos :

View More Examples of isCancelled()
   1: import java.util.concurrent.Future;
   2: import java.util.concurrent.FutureTask;
   3: import java.util.concurrent.TimeUnit;
   4:         ...
   5:     {
   6:         private static class FutureNode extends FutureTask
   7:         {
   8:         ...
   9: 
  10:         private final FutureTask future;
  11: 
  12:         ...
  13:         {
  14:             return future.isCancelled();

View Full Code Here

isDone

public boolean isDone()
Specified by:
isDone in interface Future<V>
Usages and Demos :

View More Examples of isDone()
   1: import java.util.concurrent.Future;
   2: import java.util.concurrent.FutureTask;
   3: import java.util.concurrent.TimeUnit;
   4:         ...
   5:     {
   6:         private static class FutureNode extends FutureTask
   7:         {
   8:         ...
   9: 
  10:         private final FutureTask future;
  11: 
  12:         ...
  13:         {
  14:             return future.isDone();

View Full Code Here

run

public void run()
Sets this Future to the result of computation unless it has been cancelled.
Specified by:
run in interface Runnable
Usages and Demos :

View More Examples of run()
   1: import java.util.concurrent.Future;
   2: import java.util.concurrent.FutureTask;
   3: import java.util.concurrent.TimeUnit;
   4:         ...
   5:     {
   6:         private static class FutureNode extends FutureTask
   7:         {
   8:         ...
   9:                 {
  10:                     super.run();
  11:                 }
  12:         ...
  13: 
  14:         private final FutureTask future;

View Full Code Here

runAndReset

protected boolean runAndReset()
Executes the computation without setting its result, and then resets this Future to initial state, failing to do so if the computation encounters an exception or is cancelled. This is designed for use with tasks that intrinsically execute more than once.
Returns:
true if successfully run and reset

set

protected void set(V v)
Sets the result of this Future to the given value unless this future has already been set or has been cancelled.
Parameters:
v - the value

setException

protected void setException(Throwable t)
Causes this future to report an ExecutionException with the given throwable as its cause, unless this Future has already been set or has been cancelled.
Parameters:
t - the cause of failure.