Java Future implementation example

RunMeFuture.java

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
 *
 * @author Lim, Teck Hooi
 *
 *
 */

public class RunMeFuture {
    private static final int NTHREDS = 10;

    private static int counter = 0;
    private static Random rand = new Random();

    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newFixedThreadPool(NTHREDS);

        List<Future<Integer>> futures = new ArrayList<>();
        for (int i = 0; i < 40; i++) {
            Callable<Integer> worker = new RunMeFutureCallable();
            futures.add(executor.submit(worker));
        }

        for (Future<Integer> future : futures) {
            System.out.println(future.get());
        }
        
        executor.shutdown();
    }

    static class RunMeFutureCallable implements Callable<Integer> {
        @Override
        public Integer call() throws Exception {
            int i = counter;
            Thread.sleep(rand.nextInt(1000));
            counter = i + 1;
            return counter;
        }
    }
}