java future併發獲得返回值示例

package com.jikuan.zjk.future;

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

/**
 * 試驗 Java 的 Future 用法 
 * jikuan.zjk
 */
public class FutureTest {

  public static class Task implements Callable<String> {
    public String call() throws Exception {
      String tid = String.valueOf(Thread.currentThread().getId());
      System.out.printf("Thread#%s : in call\n", tid);
      return tid;
    }
  }

  static Callable<Integer> test3 = new Callable<Integer>() {
    public Integer call() throws Exception {
      return new Random().nextInt(100);
    }
  };

  public static void main(String[] args) throws InterruptedException, ExecutionException {
    // test 1
    List<Future<String>> results = new ArrayList<Future<String>>();
    ExecutorService es = Executors.newCachedThreadPool();
    for (int i = 0; i < 100; i++)
      results.add(es.submit(new Task()));
    // get是阻塞的，等待有返回到Future中才會繼續
    for (Future<String> res : results)
      System.out.println(res.get());
    // test 2
    ExecutorService threadPool = Executors.newSingleThreadExecutor();
    Future<Integer> future = threadPool.submit(new Callable<Integer>() {
      public Integer call() throws Exception {
        return new Random().nextInt(100);
      }
    });
    System.out.println(future.get());

    // test 3
    ExecutorService fixThreadPool = Executors.newFixedThreadPool(1);
    Future<Integer> future2 = fixThreadPool.submit(test3);
    System.out.println(future2.get());
  }

}