com.diffplug.common.util.concurrent

Class ForwardingListenableFuture<V>

java.lang.Object

com.diffplug.common.collect.ForwardingObject

com.diffplug.common.util.concurrent.ForwardingFuture<V>

com.diffplug.common.util.concurrent.ForwardingListenableFuture<V>

Type Parameters:

V - The result type returned by this Future’s get method

All Implemented Interfaces:

ListenableFuture<V>, Future<V>

Direct Known Subclasses:

ForwardingCheckedFuture, ForwardingListenableFuture.SimpleForwardingListenableFuture

public abstract class ForwardingListenableFuture<V>
extends ForwardingFuture<V>
implements ListenableFuture<V>

A ListenableFuture which forwards all its method calls to another future. Subclasses should override one or more methods to modify the behavior of the backing future as desired per the decorator pattern.

Most subclasses can just use ForwardingListenableFuture.SimpleForwardingListenableFuture.

Since:

4.0

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ForwardingListenableFuture.SimpleForwardingListenableFuture<V> A simplified version of ForwardingListenableFuture where subclasses can pass in an already constructed ListenableFuture as the delegate.

Nested classes/interfaces inherited from class com.diffplug.common.util.concurrent.ForwardingFuture

ForwardingFuture.SimpleForwardingFuture<V>

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ForwardingListenableFuture() Constructor for use by subclasses.

Method Summary

Modifier and Type	Method and Description
void	addListener(Runnable listener, Executor exec) Registers a listener to be run on the given executor.
protected abstract ListenableFuture<V>	delegate()

Methods inherited from class com.diffplug.common.util.concurrent.ForwardingFuture

cancel, get, get, isCancelled, isDone

Methods inherited from class com.diffplug.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.concurrent.Future

cancel, get, get, isCancelled, isDone

Constructor Detail

ForwardingListenableFuture

protected ForwardingListenableFuture()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract ListenableFuture<V> delegate()

Specified by:

delegate in class ForwardingFuture<V>

addListener

public void addListener(Runnable listener,
                        Executor exec)

Description copied from interface: ListenableFuture

Registers a listener to be run on the given executor. The listener will run when the Future’s computation is complete or, if the computation is already complete, immediately.

There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called once the computation is complete.

Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during Executor.execute (e.g., a RejectedExecutionException or an exception thrown by direct execution) will be caught and logged.

Note: For fast, lightweight listeners that would be safe to execute in any thread, consider MoreExecutors.directExecutor(). Otherwise, avoid it. Heavyweight directExecutor listeners can cause problems, and these problems can be difficult to reproduce because they depend on timing. For example:

• The listener may be executed by the caller of addListener. That caller may be a UI thread or other latency-sensitive thread. This can harm UI responsiveness.
• The listener may be executed by the thread that completes this Future. That thread may be an internal system thread such as an RPC network thread. Blocking that thread may stall progress of the whole system. It may even cause a deadlock.
• The listener may delay other listeners, even listeners that are not themselves directExecutor listeners.

This is the most general listener interface. For common operations performed using listeners, see Futures. For a simplified but general listener interface, see addCallback().

Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.

Specified by:

addListener in interface ListenableFuture<V>

Parameters:

listener - the listener to run when the computation is complete

exec - the executor to run the listener in