java 多线程 day10 获取线程的返回值 CallableAndFuture

import java.util.Random;
import java.util.concurrent.*;

/**
 * Created by chengtao on 17/12/4.
 *
 * 获取线程的结果
 * <T> Future<T> submit(Callable<T> task);
 */
public class Thread1001_CallableAndFuture {
    public static void main(String[] args)throws Exception {
//        future01();
//        future02();
        future03();
        System.out.println("主线程 已经执行完了");
    }

    public static void future01() throws Exception{
        ExecutorService threadPool =  Executors.newFixedThreadPool(5);
        Future<String> future =
                threadPool.submit(
                        new Callable<String>() {
                            public String call() throws Exception {
                                Thread.sleep(2000);
                                return "hello";
                            };
                        }
                );
        System.out.println("等待结果");
        System.out.println("拿到结果：" + future.get());
    }

    //设置 返回任务的时间
    public static void future02() throws Exception{
        ExecutorService threadPool =  Executors.newSingleThreadExecutor();
        Future<Integer> future =
                threadPool.submit(
                        new Callable<Integer>() {
                            public Integer call() throws Exception {
                                Thread.sleep(2000);
                                return 5;
                            };
                        }
                );
        System.out.println("等待结果");
        System.out.println("拿到结果：" + future.get(1, TimeUnit.SECONDS));
    }

    //一次提交多个任务，哪个任务先执行完，就先返回哪个任务的结果
    public static void future03() throws Exception{

        ExecutorService threadPool2 =  Executors.newFixedThreadPool(10);
        CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
        for(int i=1;i<=10;i++){
            final int seq = i;
            completionService.submit(new Callable<Integer>() {
                public Integer call() throws Exception {
                    int sleepNum = new Random().nextInt(5000);
                    System.out.println("seq = " + seq + " sleep = " +  sleepNum );
                    Thread.sleep(sleepNum);
                    return seq;
                }
            });
        }
        for(int i=0;i<10;i++){
            System.out.println( completionService.take().get());
        }
    }
}