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本文轉載自：http://www.cnblogs.com/starcrm/p/5010863.html

案例1：

package com.net.thread.future;import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.FutureTask; import java.util.concurrent.TimeUnit;/*** @author * @Time：2017年8月18日 上午10:49:07* @version 1.0* @description*/ import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.FutureTask;import java.util.concurrent.TimeUnit;import java.util.concurrent.TimeoutException;public class FutureTaskExample {public static void main(String[] args) {MyCallable callable1 = new MyCallable(1000);MyCallable callable2 = new MyCallable(5000);FutureTask<String> futureTask1 = new FutureTask<String>(callable1);FutureTask<String> futureTask2 = new FutureTask<String>(callable2);ExecutorService executor = Executors.newFixedThreadPool(2);executor.execute(futureTask1);executor.execute(futureTask2);while (true) {try {if(futureTask1.isDone() && futureTask2.isDone()){System.out.println("Done");//shut down executor service executor.shutdown();return;}if(!futureTask1.isDone()){//阻塞futureTask1System.out.println("FutureTask1 output="+futureTask1.get());}if(!futureTask2.isDone()){//阻塞futureTask2System.out.println("FutureTask2 output="+futureTask2.get(1000,TimeUnit.MILLISECONDS));}} catch (InterruptedException | ExecutionException e) {e.printStackTrace();}catch(Exception e){//do nothing }}}static class MyCallable implements Callable<String> {private long waitTime;public MyCallable(int timeInMillis){this.waitTime=timeInMillis;}@Overridepublic String call() throws Exception {Thread.sleep(waitTime);return Thread.currentThread().getName();}}}

運行結果很簡單，必須是：

FutureTask1 output=pool-1-thread-1
FutureTask2 output=pool-1-thread-2
Done

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案例2：

package com.net.thread.future;import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.FutureTask; import java.util.concurrent.TimeUnit;/*** @author * @Time：2017年8月18日 上午10:49:07* @version 1.0* @description*/ public class FutureTaskExample2 {public static void main(String[] args) {MyCallable callable1 = new MyCallable(1000);MyCallable callable2 = new MyCallable(5000);FutureTask<String> futureTask1 = new FutureTask<String>(callable1);FutureTask<String> futureTask2 = new FutureTask<String>(callable2);ExecutorService executor = Executors.newFixedThreadPool(2);executor.execute(futureTask1);executor.execute(futureTask2);while (true) {try {if(futureTask1.isDone() && futureTask2.isDone()){System.out.println("Done");//shut down executor service executor.shutdown();return;}if(!futureTask1.isDone()){//阻塞futureTask1System.out.println("FutureTask1 output="+futureTask1.get());}System.out.println("Waiting for FutureTask2 to complete");String s = futureTask2.get(1000, TimeUnit.MILLISECONDS); //阻塞500毫秒if(s !=null){System.out.println("FutureTask2 output="+s);}else{System.out.println("FutureTask2 output is null");}} catch (InterruptedException | ExecutionException e) {e.printStackTrace();}catch(Exception e){//do nothing } }}static class MyCallable implements Callable<String> {private long waitTime;public MyCallable(int timeInMillis){this.waitTime=timeInMillis;}@Overridepublic String call() throws Exception {Thread.sleep(waitTime);return Thread.currentThread().getName();}}}

運行結果：

FutureTask1 output=pool-1-thread-1
Waiting for FutureTask2 to complete
Waiting for FutureTask2 to complete
Waiting for FutureTask2 to complete
Waiting for FutureTask2 to complete
FutureTask2 output=pool-1-thread-2
Done

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說明：

1、get()方法用來獲取執行結果，這個方法會產生阻塞，會一直等到任務執行完畢才返回；

2、get(long timeout, TimeUnit unit)用來獲取執行結果，如果超過指定時間，直接結束執行下面的代碼；如果是在循環中，則跳出本次循環進行下一次輪訓(continue功能類似)。

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轉載于:https://www.cnblogs.com/chen1-kerr/p/7388725.html

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