FutureTaskpublic class FutureTask extends Object implements RunnableFuture| A cancellable asynchronous computation. This class provides a base
implementation of {@link 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 {@link Callable} or
{@link java.lang.Runnable} object. Because FutureTask
implements Runnable, a FutureTask can be
submitted to an {@link 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. |
| Fields Summary |
|---|
| private final Sync | syncSynchronization control for FutureTask |
| Constructors Summary |
|---|
public FutureTask(Callable callable)Creates a FutureTask that will upon running, execute the
given Callable.
if (callable == null)
throw new NullPointerException();
sync = new Sync(callable);
| 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.
sync = new Sync(Executors.callable(runnable, result));
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| Methods Summary |
|---|
| public boolean | cancel(boolean mayInterruptIfRunning)
return sync.innerCancel(mayInterruptIfRunning);
| | 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.
| | public V | get()
return sync.innerGet();
| | public V | get(long timeout, java.util.concurrent.TimeUnit unit)
return sync.innerGet(unit.toNanos(timeout));
| | public boolean | isCancelled()
return sync.innerIsCancelled();
| | public boolean | isDone()
return sync.innerIsDone();
| | public void | run()Sets this Future to the result of its computation
unless it has been cancelled.
sync.innerRun();
| | 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.
return sync.innerRunAndReset();
| | 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.
sync.innerSet(v);
| | protected void | setException(java.lang.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.
sync.innerSetException(t);
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