Java: FutureTask demo - ConcurrencyHelper.class

gistfile1.java

package com.pelssers.futuretask;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;

public final class ConcurrencyHelper {

    public static <T> List<T> getResults(final Iterable<Callable<T>> callables, final int numberOfThreads, 
        final int sleepInMillis) throws InterruptedException, ExecutionException {
        final List<T> results = new ArrayList<T>();
        final ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
        final List<FutureTask<T>> tasks = mapToFutureTasks(callables);
        for (final FutureTask<T> task : tasks) {
            executor.execute(task);
        }
        boolean isFinished = isDone(tasks);
        while (!isFinished) {
            try {
                Thread.sleep(sleepInMillis);
                isFinished = isDone(tasks);
            } catch (final InterruptedException e) {

            }
        }

        for (final FutureTask<T> task : tasks) {
            results.add(task.get());
        }

        executor.shutdown();
        return results;

    }

    private static <T> List<FutureTask<T>> mapToFutureTasks(final Iterable<Callable<T>> callables) {
        final List<FutureTask<T>> futureTasks = new ArrayList<FutureTask<T>>();
        for (final Callable<T> callable : callables) {
            futureTasks.add(new FutureTask<T>(callable));
        }
        return futureTasks;
    }

    private static <T> boolean isDone(final Iterable<FutureTask<T>> tasks) {
        final boolean isDone = true;
        for (final FutureTask<T> task : tasks) {
            if (!task.isDone()) {
                return false;
            }
        }
        return isDone;
    }

}