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The FutureTask class implements 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.
The FutureTask class has the following
constructors:
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. |
which means that a FutureTask can be used to wrap a Callable
or Runnable object. Because FutureTask
implements Runnable, it can be supplied to a Thread instance to
run within a thread.
In addition to implementing the methods specified in the Future
interface, the FutureTask class implements the following methods:
protected
void |
done()
Protected
method invoked when this task transitions to state isDone
(whether normally or via cancellation). |
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. |
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