cz.cuni.amis.utils.future
Class FlagFuture<Result,FlagType>

java.lang.Object
  cz.cuni.amis.utils.future.FlagFuture<Result,FlagType>

Type Parameters:

Result -

FlagType -

All Implemented Interfaces:

FlagListener<FlagType>, IFuture<Result>, java.util.concurrent.Future<Result>, java.util.EventListener

public class FlagFuture<Result,FlagType>
extends java.lang.Object
implements IFuture<Result>, FlagListener<FlagType>

Future implementation that is listening on a flag and when it's terminal state is set on the flag the future completes itself with result specified in the map (under the key of the flag value).

Thread-safe implementation, not as easy as it seems ;-)

Nested Class Summary

Nested classes/interfaces inherited from interface cz.cuni.amis.utils.flag.FlagListener

FlagListener.FlagListenerNotifier<T>

Constructor Summary

FlagFuture(Flag<FlagType> waitFlag, FlagType terminalFlagValue, Result resultValue)
Initializing future to wait for 'terminalFlagValue' at 'waitFlag', when that happens complete itself with result 'resultValue'.

FlagFuture(Flag<FlagType> waitFlag, java.util.Map<FlagType,Result> terminalMap)
In constructor you have to specify a flag where the future should listen at + terminal states for the future (terminalMap).

Method Summary

boolean	cancel(boolean mayInterruptIfRunning)
void	flagChanged(FlagType changedValue)
Result	get() Waits if necessary for the computation to complete, and then retrieves its result.
Result	get(long timeout, java.util.concurrent.TimeUnit unit) Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.
boolean	isCancelled()
boolean	isDone()
void	stop(Result result) Stops the future (not the task it represents!).

Methods inherited from class java.lang.Object

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

Constructor Detail

FlagFuture

public FlagFuture(Flag<FlagType> waitFlag,
                  java.util.Map<FlagType,Result> terminalMap)

In constructor you have to specify a flag where the future should listen at + terminal states for the future (terminalMap).

Possible flag values and the behavior of the future:

1. flag value is in the keys of terminalMap - the future completes with the result under the key from the flag
2. flag value is not in the keys of terminalMap - the future ignores that value and waits for next flag change

Note that the flag value is examined during the construction of the object and if the flag has value that is in the terminalMap the future is completes itself.

Parameters:

waitFlag -

terminalMap -

FlagFuture

public FlagFuture(Flag<FlagType> waitFlag,
                  FlagType terminalFlagValue,
                  Result resultValue)

Initializing future to wait for 'terminalFlagValue' at 'waitFlag', when that happens complete itself with result 'resultValue'.

Parameters:

waitFlag -

terminalFlagValue -

resultValue -

Method Detail

stop

public void stop(Result result)

Stops the future (not the task it represents!). It raise the latch unblocking all threads waiting for the future to complete. Sets the result to desired value.

Note that this happened IFF !isDone(), e.g. if the future is already done this won't do anything (as latch is already raised and the result value has been determined).

Note that this is different behavior that cancel() should implement, therefore it's a different method.

cancel

public boolean cancel(boolean mayInterruptIfRunning)

Specified by:

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

get

public Result get()

Description copied from interface: IFuture

Waits if necessary for the computation to complete, and then retrieves its result.

Specified by:

get in interface IFuture<Result>

Specified by:

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

Returns:

the computed result

get

public Result get(long timeout,
                  java.util.concurrent.TimeUnit unit)

Description copied from interface: IFuture

Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.

Specified by:

get in interface IFuture<Result>

Specified by:

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

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

the computed result

isCancelled

public boolean isCancelled()

Specified by:

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

isDone

public boolean isDone()

Specified by:

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

flagChanged

public void flagChanged(FlagType changedValue)

Specified by:

flagChanged in interface FlagListener<FlagType>