java8学习：CompletableFuture方法使用
下面是自己总结的一部分的api的使用,当然下面有些方法后面加上Async就会变为异步的 /** * 变换:参数为Function接口 * thenApply:将上一个结果当做这次thenApply的参数传入,加以处理后,返回一个值 * 可以传入T返回T也可以传入T返回U */ public void thenApply() { CompletableFuture<String> future = CompletableFuture.supplyAsync(()-> 1).thenApply(i -> String.valueOf(i)); String i = future.join(); System.out.println(i); //1 } /** * 消费 * 参数为Consumer接口 * thenAccept:将上一个的结果当做这次的参数传入,但是无返回值 */ public void thenAccept() { CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> 1).thenAccept((integer -> System.out.println(integer))); future.join(); //1 } public void thenCompose() { CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> 1) //提供第一个CompletableFuture结果值 .thenCompose((i) -> //将上一个结果值传入下一个CompletableFuture CompletableFuture.supplyAsync(() -> i + 2)); //对传入的结果值进行处理 Integer join = future.join(); System.out.println(join); } /** * 结合两个结果得到一个最终值 * 逻辑处理需要的是BiFunction接口 * 需要两个CompletableFuture结果,并且需要有处理两个结果的逻辑 * 两个CompletableFuture返回的结果不需要一致 */ public void thenCombine() { CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello ") //第一个CompletableFuture返回结果 .thenCombine(CompletableFuture.supplyAsync(() -> 1), //第二个CompletableFuture返回结果 (future1, future2) -> future1 + future2); //处理两个结果的逻辑 String join = future.join(); System.out.println(join); //Hello World } /** * 跟上面的差不多,只不过这里处理逻辑需要的是一个BiConsumer接口,无返回值而已 */ public void thenAcceptBoth() { CompletableFuture<Void> both = CompletableFuture.supplyAsync(() -> "Hello ") //第一个CompletableFuture返回结果 .thenAcceptBoth(CompletableFuture.supplyAsync(() -> "World"), //第二个CompletableFuture返回结果 (future1, future2) -> System.out.println(future1 + future2));//处理两个结果的逻辑 both.join(); //Hello World } /** * 两个CompletableFuture一起执行,哪个先执行完就用哪个CompletableFuture的结果 * 处理逻辑需要的参数是一个Function接口 * 下面整体代码的逻辑是返回1的睡眠一秒,返回2的睡眠0.3秒,所以返回2的肯定比1要快,所以结果为2,然后应用到处理逻辑上 * 最终结果就是为 2 done * 两个CompletableFuture返回的参数需要一致 * 这适用于两种渠道完成同一个事情，就可以调用这个方法，找一个最快的结果进行处理，最终有返回值。 */ public void applyToEither() { CompletableFuture<String> apply = CompletableFuture.supplyAsync(() -> { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return "1"; }).applyToEither( CompletableFuture.supplyAsync(() -> { try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } return "2"; }), (future) -> future + " done" //对于首先完成的CompletableFuture任务之后执行的逻辑 ); String join = apply.join(); System.out.println(join);//2 done } /** * 与上面使用方法一致,只是多加了一个选项 * 结果为3 three */ public void applyToEithers() { CompletableFuture<String> apply = CompletableFuture.supplyAsync(() -> { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return "1"; }).applyToEither( CompletableFuture.supplyAsync(() -> { try { Thread.sleep(800); } catch (InterruptedException e) { e.printStackTrace(); } return "2"; }),(future) -> future + " done" //对于首先完成的CompletableFuture任务之后执行的逻辑 ).applyToEither( CompletableFuture.supplyAsync(() -> { try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } return "3"; }),(future -> future + " three") ); String join = apply.join(); System.out.println(join);//2 done } /** * 对于出错的处理过程进行补偿,即如果future出错,会运行exceptionally里的Function函数 * 当然没有错就不会运行后面指定的函数 */ @Test public void exceptionally() { CompletableFuture<String> exceptionally = CompletableFuture.supplyAsync(() -> { int i = 1 / 0 ; return "1"; }).exceptionally(ex -> { ex.printStackTrace(); return "error"; }); String join = exceptionally.join(); System.out.println(join); } /** * 输出 * error * java.util.concurrent.CompletionException: java.lang.ArithmeticException: / by zero * at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273) * at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280) * at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1592) * at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1582) * at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289) * at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056) * at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692) * at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157) * Caused by: java.lang.ArithmeticException: / by zero * at com.qidai.demotest.MyTestx.lambda$exceptionally$18(MyTestx.java:125) * at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590) * ... 5 more */ /** * 与上面的thenAccept相比较,这个方法并不需要输入参数,相同点是都是无返回值 */ public void thenRun() { CompletableFuture<Void> runnable = CompletableFuture.supplyAsync(() -> "1").thenRun(() -> System.out.println("runnable")); runnable.join(); }
