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java.util.concurrent
Class FutureTask
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public class FutureTask<V>
implements RunnableFuture<V>
Type Parameters:
  • V - The result type returned by this FutureTask's get method
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.

Since1.5
VersionNot specified.
AuthorDoug Lea
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Constructor Summary
FutureTask( Callable<V> 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 )
No description provided.
protected void done()
Protected method invoked when this task transitions to state isDone (whether normally or via cancellation).
V get()
No description provided.
V get( long timeout, TimeUnit unit )
No description provided.
boolean isCancelled()
No description provided.
boolean isDone()
No description provided.
void run()
Sets this Future to the result of its 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 java.langObject
Constructor Detail
FutureTask
public FutureTask ( Callable<V> callable )
Creates a FutureTask that will, upon running, execute the given Callable.
Parameters
TypeNameDescription
Callable<V> callable the callable task
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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
TypeNameDescription
Runnable runnable the runnable task
V 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)
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Method Detail
cancel
public boolean cancel ( boolean mayInterruptIfRunning )
No description provided.
Implements method in Future
Parameters
TypeNameDescription
boolean mayInterruptIfRunning No description provided.
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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.
Returns void No description provided.
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get
public V get ( )
throws
No description provided.
Implements method in Future
Exceptions
ExecutionException No description provided.
InterruptedException No description provided.
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get
public V get ( long timeout, TimeUnit unit )
throws
No description provided.
Implements method in Future
Parameters
TypeNameDescription
long timeout No description provided.
TimeUnit unit No description provided.
Exceptions
InterruptedException No description provided.
ExecutionException No description provided.
TimeoutException No description provided.
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isCancelled
public boolean isCancelled ( )
No description provided.
Implements method in Future
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isDone
public boolean isDone ( )
No description provided.
Implements method in Future
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run
public void run ( )
Sets this Future to the result of its computation unless it has been cancelled.
Implements method in Runnable
Returns void No description provided.
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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.
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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. This method is invoked internally by the run method upon successful completion of the computation.
Parameters
TypeNameDescription
V v the value
Returns void No description provided.
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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. This method is invoked internally by the run method upon failure of the computation.
Parameters
TypeNameDescription
Throwable t the cause of failure
Returns void No description provided.
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