Future offers you method isDone() which is not blocking and returns true if computation has completed, false otherwise. Future.get() is used to retrieve the result of computation. You have a couple of options: call isDone() and if the result is ready ask for it by invoking get(), notice how there is no blocking block indefinitely … Read more
One of the possible solutions I’ve just found: public class BoundedExecutor { private final Executor exec; private final Semaphore semaphore; public BoundedExecutor(Executor exec, int bound) { this.exec = exec; this.semaphore = new Semaphore(bound); } public void submitTask(final Runnable command) throws InterruptedException, RejectedExecutionException { semaphore.acquire(); try { exec.execute(new Runnable() { public void run() { try { … Read more
Define a callback interface to receive whatever parameters you want to pass along in the completion notification. Then invoke it at the end of the task. You could even write a general wrapper for Runnable tasks, and submit these to ExecutorService. Or, see below for a mechanism built into Java 8. class CallbackTask implements Runnable … Read more