how to convert java Future<V> to guava ListenableFuture<V>

java concurrency guava futuretask
justatester picture justatester · May 11, 2015 · Viewed 7.7k times · Source

I need to find a way to convert from Future to ListenableFuture. Currently i'm using a service which returns Future but i need to hook up a listener to it. I can't change the service interface as it doesn't belong to me.

Is there a simple way to do that ?

I have read guava docs but still i can't find a way to do it.

Answer

qwwdfsad picture qwwdfsad · May 11, 2015

Guava provides the JdkFutureAdapters types for this conversion. The API states

Utilities necessary for working with libraries that supply plain Future instances.

For example

Future<?> future = ...;
ListenableFuture<?> listenable = JdkFutureAdapters.listenInPoolThread(future);

But you should use it with care: it's hard to emulate listenable future when you already have submitted task, because there is no way to put a hook on completion there, so Guava takes a new thread and blocks there until original Future is completed.

The Guava Wiki also contains some information on this specific case.

Related questions

Atomically incrementing counters stored in ConcurrentHashMap

I would like to collect some metrics from various places in a web app. To keep it simple, all these will be counters and therefore the only modifier operation is to increment them by 1. The increments will be concurrent and …

Read More
How to wait for all threads to finish, using ExecutorService?

I need to execute some amount of tasks 4 at a time, something like this: ExecutorService taskExecutor = Executors.newFixedThreadPool(4); while(...) { taskExecutor.execute(new MyTask()); } //...wait for completion somehow How can I get notified once all of them are complete? For now …

Read More
What's the difference between ConcurrentHashMap and Collections.synchronizedMap(Map)?

I have a Map which is to be modified by several threads concurrently. There seem to be three different synchronized Map implementations in the Java API: Hashtable Collections.synchronizedMap(Map) ConcurrentHashMap From what I understand, Hashtable is an old implementation (…

Read More