CompletableFuture 简介和使用

前言：Futrue的缺点有（1）get方法会阻塞 ，（2）不支持注册回调方法 ，（3）不支持级联操作

CompletableFuture弥补了这些缺点

 

直接上代码：

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public class CompletableFutureTest {       public static void main(String[] args) throws Exception {   //        test1(); //        test2(); //        test3();           test4();     }         //采用了callable+ future方式  ,get方法获取任务的返回值会被阻塞住     public  static  void  test1() throws  Exception {         ExecutorService executor = Executors.newCachedThreadPool();         Future<String> result = executor.submit(()->{             //模拟执行耗时任务             System.out.println("task doing...");             try {                 Thread.sleep(3000);             } catch (InterruptedException e) {                 e.printStackTrace();             }             //返回结果             return "result";         });         //这里只是将空闲的线程中断，将线程池的状态改为shutdown,不能继续往线程池中添加任务         executor.shutdown();         System.out.println("task运行结果" + result.get());     }       //采用了competableFuture，采用回调的方式获取任务的返回值     public static void test2() throws Exception {         //supplyAsync内部使用ForkJoinPool线程池执行任务         CompletableFuture<String> completableFuture=CompletableFuture.supplyAsync(()->{             //模拟执行耗时任务             System.out.println("task doing...");             try {                 Thread.sleep(3000);             } catch (InterruptedException e) {                 e.printStackTrace();             }             //返回结果             return "100";         }).whenComplete((v,r)->{             System.out.println("计算结果是: "+v);         });         //CompletableFuture里使用的线程池里的线程默认是daemon的。main线程结束后，整个程序也         //结束了，这里将main线程join后任务里的代码才可以执行完          Thread.currentThread().join();     }         //compeltableFuture可以支持级联操作     public static void test3() throws Exception {         IntStream.range(1,10).boxed().forEach( i ->  CompletableFuture.supplyAsync(CompletableFutureTest::get)                 .thenAccept(CompletableFutureTest::display)                 .whenComplete((v,r)->                     System.out.println(i +" have done")                 )         );         Thread.currentThread().join();     }       public static  void display(int data){         int value = ThreadLocalRandom.current().nextInt(10);         try {             System.out.println(Thread.currentThread().getName() +"  display  data "+ data+" will sleep "+value);             TimeUnit.SECONDS.sleep(value);         } catch (InterruptedException e) {             e.printStackTrace();         }         System.out.println(Thread.currentThread().getName() +"  dispaly have done  with  data =  "+data);     }         public static  int get(){         int value = ThreadLocalRandom.current().nextInt(10);         try {             System.out.println(Thread.currentThread().getName() +"  get will sleep "+value);             TimeUnit.SECONDS.sleep(value);         } catch (InterruptedException e) {             e.printStackTrace();         }         System.out.println(Thread.currentThread().getName() +"  get have done  "+value);         return value;     }       //两个线程分别执行任务，任务都执行完后再执行最后的runnable     public static void test4() throws InterruptedException {         CompletableFuture.supplyAsync(Object::new)                 .thenAcceptAsync(obj -> {                     try {                         System.out.println("obj ====== start");                         TimeUnit.SECONDS.sleep(5);                         System.out.println("obj ====== " + obj);                     } catch (InterruptedException e) {                         e.printStackTrace();                     }         }).runAfterBoth(CompletableFuture.supplyAsync(() -> "hello")                 .thenAcceptAsync((v) -> {                     try {                         System.out.println("string ====== start");                         TimeUnit.SECONDS.sleep(3);                         System.out.println("string ====== " + v);                     } catch (InterruptedException e) {                         e.printStackTrace();                     }                 }), () -> System.out.println("finished"));         Thread.currentThread().join();     }           //一个线程计算奇数和，一个线程计算偶数和，main线程将他们相加     public static  void test9() throws ExecutionException, InterruptedException {         CompletableFuture<Integer> oddNumber = CompletableFuture.supplyAsync(()->{             try {                 System.out.println("开始计算奇数和  ...");                 Thread.sleep(3_000);                 System.out.println("结束计算奇数和  ...");             } catch (InterruptedException e) {                 e.printStackTrace();             }             return   1+3+5+7+9;         });         CompletableFuture<Integer> evenNumber = CompletableFuture.supplyAsync(()->{             try {                 System.out.println("开始计算偶数和  ...");                 Thread.sleep(5_000);                 System.out.println("结束计算偶数和  ...");             } catch (InterruptedException e) {                 e.printStackTrace();             }             return 2+4+6+8;         });         long startTime = System.currentTimeMillis();         CompletableFuture<Integer> resultFuturn = oddNumber.thenCombine(evenNumber,(odd,even)->{             return odd + even;         });         System.out.println("===============");         System.out.println("运行结果是："+resultFuturn.get()+" 总共耗时："+ (System.currentTimeMillis()-startTime) +"毫秒");     }   }

　　

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本文作者：veblenJan°
本文链接：https://www.cnblogs.com/veblen/p/13071689.html
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