CompletableFuture学习

//supplyAsync 和 runAsync 区别在前个有返回值，后一个没有返回值 public static void supplyAsync() throws ExecutionException, InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); // executorService.submit(() -> { // System.out.println("executorService 是否为守护线程 :" + Thread.currentThread().isDaemon()); // return null; // }); CompletableFuture<String> completableFuture1=CompletableFuture.supplyAsync(()->{ System.out.println("this is lambda supplyAsync"); System.out.println("supplyAsync 是否为守护线程 " + Thread.currentThread().isDaemon()); try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } return "result1"; }); CompletableFuture<String> completableFuture2=CompletableFuture.supplyAsync(()->{ System.out.println("this is executorService"); System.out.println("executorService supplyAsync 是否为守护线程 " + Thread.currentThread().isDaemon()); try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } return "result2"; },executorService); System.out.println(completableFuture1.get()); System.out.println(completableFuture2.get()); executorService.shutdown(); } //这两个方法的入参是一个completableFuture组、allOf就是所有任务都完成时返回。但是是个Void的返回值。 //anyOf是当入参的completableFuture组中有一个任务执行完毕就返回。返回结果是第一个完成的任务的结果 public static void of() throws ExecutionException, InterruptedException { CompletableFuture<String> completableFuture1=CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); } return "result1"; }); CompletableFuture<String> completableFuture2=CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } return "result2"; }); CompletableFuture allOf = CompletableFuture.allOf(completableFuture1,completableFuture2); System.out.println(allOf.get()); CompletableFuture anyOf = CompletableFuture.anyOf(completableFuture1,completableFuture2); System.out.println(anyOf.get()); } //这个方法是执行这个方法的时候任务执行完了就返回任务的结果，如果任务没有执行完就返回你的入参。 public static void getNow() throws ExecutionException, InterruptedException { CompletableFuture<String> completableFuture1=CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); } return "result1"; }); System.out.println(completableFuture1.getNow("222"));//输出:222 } /* whenComplete：如果调用whenComplete的中途，还发生了其他事情，图中的主线程的sleep(400)；导致completableFuture这个任务执行完毕了， 那么就使用主线程调用。如果调用的中途没有发生其他任务且在触碰到whenComplete方法时completableFuture这个任务还没有彻底执行完毕那么就会用completableFuture这个任务所使用的线程。 whenCompleteAsync： 异步执行 */ public static void whenXXX() throws ExecutionException, InterruptedException { CompletableFuture<String> completableFuture1=CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread()); return "result1"; }).whenCompleteAsync((result,ex)->{ System.out.println(result+"-"+ex+"-"+Thread.currentThread()); }); System.out.println("-"+Thread.currentThread()); try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(completableFuture1.get()+"-"+Thread.currentThread()); } /* 使用任务的线程接着执行后续的操作 thenCompose: 上一个任务结果是then的一部分 thenCombine: 2个任务的结果合并到一个方法里 thenApply: 有入参有返回值类型的 thenAccept : 有入参没有返回值类型 */ public static void thenXXX() throws ExecutionException, InterruptedException { CompletableFuture<String> completableFuture1=CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread()); return "result1"; }); CompletableFuture<String> thenCompose=completableFuture1.thenCompose(s -> CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(s+"-"+Thread.currentThread()); return s+":"+"thenCompose"; }));//s=="result1" CompletableFuture<String> thenCombine=completableFuture1.thenCombine( CompletableFuture.supplyAsync(()->{ try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("thenCombine"+"-"+Thread.currentThread()); return "thenCombine"; }),(s1,s2)-> s1+":"+s2 );//2个任务的结果合并到一个方法里 System.out.println(completableFuture1.get()); System.out.println(thenCompose.get()); System.out.println(thenCombine.get()); }