CompletableFuture API用法介绍(二)

文章目录

一、纯消费 API
1、thenAccep
- 2、thenAcceptBoth
- 3、runAfterBoth
- 4、thenRun(Runnable action)
二、组合API
- 1、thenCompose
- 2、thenCombine
三、acceptEither / applyToEither
- 1、 acceptEither
- 3、 applyToEither
四、allOf / anyOf
- 1、allOf
- 2、anyOf

上一篇文章介绍部分API CompletableFuture API用法介绍(一)，这篇继续讲解CompletableFuture 其它API用法。

一、纯消费 API

单纯的去消费结果而不会返回新的值，因些计算结果为 Void;

1、thenAccep

public CompletableFuture thenAccept(Consumer<? super T> action)
public CompletableFuture thenAcceptAsync(Consumer<? super T> action)
public CompletableFuture thenAcceptAsync(Consumer<? super T> action, Executor executor)】

public static void completableFuturThenAccep()throws Exception {CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> 10).thenAccept(System.out::println) //消费 上一级返回值 10.thenAcceptAsync(System.out::println); //上一级没有返回值 输出nullSystem.out.println(future.get());//null}

2、thenAcceptBoth

public CompletableFuture thenAcceptBoth(CompletionStage<? extends U> other, BiConsumer<? super T,? super U> action)
public CompletableFuture thenAcceptBothAsync(CompletionStage<? extends U> other, BiConsumer<? super T,? super U> action)
public CompletableFuture thenAcceptBothAsync(CompletionStage<? extends U> other, BiConsumer<? super T,? super U> action, Executor executor)

thenAccept 相比，参数类型多了一个 CompletionStage<? extends U> other,以上方法会接收上一个CompletionStage返回值，和当前的一个。

public static void complateFuturThenAcceptBoth() throws Exception {CompletableFuture.supplyAsync(() -> 10).thenAcceptBoth(CompletableFuture.supplyAsync(() -> 20), (a, b) -> {System.out.println(a);System.out.println(b);}).get();}

3、runAfterBoth

runAfterBoth 和以上方法不同，传一个 Runnable 类型的参数，不接收上一级的返回值

public CompletableFuture runAfterBoth
public CompletableFuture runAfterBothAsync
public CompletableFuture runAfterBothAsync

public static void complateFuturRunAfterBoth() throws Exception {   System.out.println("开始");CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> {System.out.println(10);return 10;}).runAfterBoth(CompletableFuture.supplyAsync(() -> {System.out.println(20);return 20;}), () -> System.out.println("开始运行run"));System.out.println(future.get());}

4、thenRun(Runnable action)

thenRun它的入参是一个Runnable的实例，表示当得到上一步的结果时的操作。

public CompletionStage thenRun(Runnable action);
public CompletionStage thenRunAsync(Runnable action);
public CompletionStage thenRunAsync(Runnable action,Executor executor);

public static void complateFuturThenRun() throws Exception {CompletableFuture.supplyAsync(() -> {try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}return "hello";}).thenRun(() -> System.out.println("hello world"));while (true){}}

二、组合API

1、thenCompose

public CompletableFuture thenCompose(Function<? super T,? extends CompletionStage> fn)
public CompletableFuture thenComposeAsync(Function<? super T,? extends CompletionStage> fn)
public CompletableFuture thenComposeAsync(Function<? super T,? extends CompletionStage> fn, Executor executor)

以上接收类型为 Function<? super T,? extends CompletionStage> fn ,fn 接收上一级返回的结果，并返回一个新的 CompletableFuture

 public static void complateFuturThenCompose() throws Exception {CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> 1).thenApply((a) -> {try {Thread.sleep(1000);} catch (InterruptedException e) {}return a + 10;}).thenCompose((s) -> {System.out.println(s); //11return CompletableFuture.supplyAsync(() -> s * 5);});System.out.println(future.get());//55}
}

2、thenCombine

public <U,V> CompletableFuture thenCombine(CompletionStage<? extends U> other, BiFunction<? super T,? super U,? extends V> fn)
public <U,V> CompletableFuture thenCombineAsync(CompletionStage<? extends U> other, BiFunction<? super T,? super U,? extends V> fn)
public <U,V> CompletableFuture thenCombineAsync(CompletionStage<? extends U> other, BiFunction<? super T,? super U,? extends V> fn, Executor executor)

两个CompletionStage是并行执行的，它们之间并没有先后依赖顺序，other并不会等待先前的CompletableFuture执行完毕后再执行。

thenCombine 和 supplyAsync 不一定哪个先哪个后，是并行执行的。

public static void complateFuturThenCombine() throws Exception {Random random = new Random();CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println("supplyAsync");return 2;}).thenApply((a) -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println("thenApply");return a * 3;}).thenCombine(CompletableFuture.supplyAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println("thenCombineAsync");return 10;}), (a, b) -> {System.out.println(a);System.out.println(b);return a + b;});System.out.println(future.get());}

三、acceptEither / applyToEither

1、 acceptEither

public CompletableFuture acceptEither(CompletionStage<? extends T> other, Consumer<? super T> action)
public CompletableFuture acceptEitherAsync(CompletionStage<? extends T> other, Consumer<? super T> action)
public CompletableFuture acceptEitherAsync(CompletionStage<? extends T> other, Consumer<? super T> action, Executor executor)

acceptEither方法是当任意一个 CompletionStage 完成的时候，action 这个消费者就会被执行。这个方法返回 CompletableFuture

 public static void complateFuturAcceptEither() throws Exception {Random random = new Random();CompletableFuture.supplyAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}return "A";}).acceptEither(CompletableFuture.supplyAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}return "B";}), System.out::println).get();}

以上代码有时输出A，有时输出B，哪个Future先执行完就会根据它的结果计算。

3、 applyToEither

总会碰到有两种渠道完成同一个事情，所以就可以调用这个方法，找一个最快的结果进行处理。

public CompletionStage applyToEither(CompletionStage<? extends T> other,Function<? super T, U> fn);
public CompletionStage applyToEitherAsync(CompletionStage<? extends T> other,Function<? super T, U> fn);
public CompletionStage applyToEitherAsync(CompletionStage<? extends T> other,Function<? super T, U> fn,Executor executor);

 public static void complateFuturApplyToEitherr() throws Exception {String result = CompletableFuture.supplyAsync(() -> {try {Thread.sleep(3000);} catch (InterruptedException e) {e.printStackTrace();}return "s1";}).applyToEither(CompletableFuture.supplyAsync(() -> {try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}return "hello world";}), s -> s).join();System.out.println(result);}

acceptEither 没有返回值，applyToEither 有返回值

四、allOf / anyOf

1、allOf

public static CompletableFuture allOf
这个方法的意思是把有方法都执行完才往下执行，没有返回值

 public static void complateFuturAllOf() throws Exception {Random random = new Random();CompletableFuture.allOf(CompletableFuture.runAsync(() -> {try {Thread.sleep(random.nextInt(5000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println(1);}),CompletableFuture.runAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println(2);})).get();}

2、anyOf

public static CompletableFuture anyOf(CompletableFuture<?>… cfs)
任务一个方法执行完都往下执行，返回一个Object类型的值

public static void complateFuturAnyOf() throws Exception {Random random = new Random();Object o = CompletableFuture.anyOf(CompletableFuture.runAsync(() -> {try {Thread.sleep(random.nextInt(4000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println(1);}),CompletableFuture.runAsync(() -> {try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}System.out.println(2);})).get();System.out.println(o);}

以上就是CompletableFuture API的基本用法，根据业务灵活组合使用。对我们的编程会很有帮助。