Java concurrency - avoid busy wait using ExecutorService and Future

In this article we would like to show to to avoid busy wait in java using ExecutorService and Future.

import com.google.common.util.concurrent.ThreadFactoryBuilder;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

public class TaskExecutorWithFuture {

    private final ExecutorService executor = Executors.newFixedThreadPool(2,
            new ThreadFactoryBuilder().setNameFormat("task-executor-%d").build()
    );

    private void executeTasks() throws InterruptedException, ExecutionException {

        Future<String> task1 = executor.submit(() -> {
            simulateTask(300);
            System.out.println(getThreadName() + " - Task 1 done");
            return "Results from task 1";
        });

        Future<String> task2 = executor.submit(() -> {
            simulateTask(100);
            System.out.println(getThreadName() + " - Task 2 done");
            return "Results from task 2";
        });

        System.out.println(getThreadName() + " - waiting for 2 tasks to be completed");
        String result1 = task1.get();
        String result2 = task2.get();
        System.out.println(getThreadName() + " - 2 tasks done");

        executor.shutdown();
    }

    private String getThreadName() {
        return Thread.currentThread().getName();
    }

    private void simulateTask(int timeout) {
        sleep(timeout);
    }

    private void sleep(int timeout) {
        try {
            TimeUnit.MILLISECONDS.sleep(timeout);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        new TaskExecutorWithFuture().executeTasks();
    }
}

Output:

main - waiting for 2 tasks to be completed
task-executor-1 - Task 2 done
task-executor-0 - Task 1 done
main - 2 tasks done

See also

1. What is busy waiting lock?