CompletableFuture串联多个异步任务实践

　　java 多线程中对于一个任务A完成了，任务B才开始；任务B完成了，任务C才开始；’任务C完成，任务D才开始；每个任务都是一个异步任务列。

废话少说，直接看代码，调试理解

    static ThreadPoolExecutor executor = new ThreadPoolExecutor(Runtime.getRuntime().availableProcessors() * 2,(int)(Runtime.getRuntime().availableProcessors() /0.1), 120,TimeUnit.SECONDS, new ArrayBlockingQueue<>(2000));public static void main(String[] args) {List<Integer> numberList = IntStream.rangeClosed(1, 10).boxed() // 将int转换为Integer
                .toList();CompletableFuture<Void> voidCompletableFuture = taskA(numberList).thenRun(() -> taskB(numberList).join()) // 此处和下面两行可以去掉join()测试观察异同.thenRun(() -> taskC(numberList).join()).thenRun(() -> taskD(numberList).join()).thenRunAsync(() -> {executor.shutdown();});// voidCompletableFuture.join();  
    }private static CompletableFuture<Void> taskD(List<Integer> numberList) {System.out.println();List<CompletableFuture<Void>> futureList = numberList.stream().map(x -> CompletableFuture.runAsync(() -> {try {Thread.sleep(2000);System.out.print("taskD--" + x);} catch (InterruptedException e) {throw new RuntimeException(e);}}, executor)).toList();return CompletableFuture.allOf(futureList.toArray(new CompletableFuture[0]));}private static CompletableFuture<Void> taskC(List<Integer> numberList) {System.out.println();List<CompletableFuture<Void>> futureList = numberList.stream().map(x -> CompletableFuture.runAsync(() -> {try {Thread.sleep(2000);System.out.print("taskC--" + x);} catch (InterruptedException e) {throw new RuntimeException(e);}}, executor)).toList();return CompletableFuture.allOf(futureList.toArray(new CompletableFuture[0]));}private static CompletableFuture<Void> taskB(List<Integer> numberList) {System.out.println();List<CompletableFuture<Void>> futureList = numberList.stream().map(x -> CompletableFuture.runAsync(() -> {try {Thread.sleep(2000);System.out.print("taskB--" + x);} catch (InterruptedException e) {throw new RuntimeException(e);}}, executor)).toList();return CompletableFuture.allOf(futureList.toArray(new CompletableFuture[0]));}private static CompletableFuture<Void> taskA(List<Integer> numberList) {System.out.println();List<CompletableFuture<Void>> futureList = numberList.stream().map(x -> CompletableFuture.runAsync(() -> {try {Thread.sleep(2000);System.out.print("taskA--" + x);} catch (InterruptedException e) {throw new RuntimeException(e);}}, executor)).toList();return CompletableFuture.allOf(futureList.toArray(new CompletableFuture[0]));}

执行结果