Java多线程之Future，有返回值的线程

import java.util.concurrent.ExecutorService;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;

public class Future {

    public static void main(String[] args) throws Exception,InterruptedException {

        java.util.concurrent.FutureTask<Integer> task = new FutureTask<>(() -> {
            TimeUnit.MILLISECONDS.sleep(5000);
            return 200;
        });

        new Thread(task).start();

        System.out.println(task.get()); //阻塞 知道线程执行完毕返回结果

        ExecutorService service = java.util.concurrent.Executors.newFixedThreadPool(5);
        java.util.concurrent.Future<Integer> result = service.submit(() -> {
            TimeUnit.SECONDS.sleep(1);
            return 200;
        });

        System.out.println(result.isDone());
        System.out.println(result.isDone()); //任务执行完没有
        System.out.println(result.get()); //阻塞等着结果
        System.out.println(result.isDone());

        service.shutdown(); //记得关掉线程池不然Java虚拟机不会自己关闭
    }

}