Simple Java example of using Executor Services

T_ExecutorService.java

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;
 
public class T_ExecutorService {
	public static void main(String[] args) throws InterruptedException {
		ExecutorService ex = Executors.newFixedThreadPool(20);
		System.out.printf("! Creating Executing service: %s%n", ex.getClass().getName());
 
		System.out.println("! Submitting tasks");
 
		List<Future<Integer>> results = new ArrayList<>();
 
		for (int i = 0; i < 10; i++) {
			results.add(ex.submit(new FooTask(i)));
			Thread.sleep(ThreadLocalRandom.current().nextInt(100));
		}
 
		System.out.println("! Tast submitting done");
 
		while (results.size() > 0) {
			Future<Integer> remove_candidate = null;
 
			for (Future<Integer> result : results) {
 
				if (result.isDone()) {
					try {
						System.out.printf("Got result: %d%n", result.get());
						remove_candidate = result;
 
					} catch (ExecutionException e) {
						e.printStackTrace();
					}
				}
			}
 
			if (remove_candidate != null) results.remove(remove_candidate);
 
			Thread.sleep(100);
		}
 
		System.out.println("! All task finished");
 
		ex.shutdown();
	}
}
 
 
class FooTask implements Callable<Integer> {
	int tmp = 0;
	int bar = 0;
	ThreadLocalRandom random;
 
	public FooTask(int bar) {
		this.bar = bar;
		this.random = ThreadLocalRandom.current();
 
		System.out.printf("+ Created task: %d%n", this.bar);
	}
 
	@Override
	public Integer call() throws Exception {
		for (; ; ) {
			this.tmp++;
//			System.out.printf("\t\tThread: \t#%d  \t\t%d%n", this.bar, this.tmp);
 
			if (random.nextInt(100) == 0) {
				System.out.printf("- Thread: %d completted%n", this.bar);
				return tmp;
			}
 
			Thread.sleep(random.nextInt(100));
		}
	}
}