JUC-CompletableFuture的常用方法

1.获得结果和触发计算

 

2.对计算结果进行处理

thenApply()和handle()的区别就是异常的处理方式不同

    public static void main(String[] args) {
        Integer result = CompletableFuture.supplyAsync(() -> {
            return 1;
        }, executor).thenApply((f -> {
            return f + 2;
        })).thenApply(f -> {
            return f + 3;
        }).thenApply(f -> {
            return f + 4;
        }).whenComplete((v, e) -> {
            if (e == null) {
                System.out.println("=== result: " + v);
            }
        }).exceptionally(e -> {
            e.printStackTrace();
            System.out.println(e.getMessage());
            return null;
        }).join();

        executor.shutdown();
    }

xxx() 和 xxxAsync() 的区别，一般用xxx()

3.对计算结果进行消费

thenAccept()和thenApply()就是有无返回值的区别

4.对计算结果进行选用

最快返回输出的线程结果作为下一次任务的输入

    public static void main(String[] args) {
        Integer join = CompletableFuture.supplyAsync(() -> {
            try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); }
            return 3;
        }, executor).applyToEither(CompletableFuture.supplyAsync(() -> {
            try { TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); }
            return 2;
        }), r -> {
            return r;
        }).applyToEither(CompletableFuture.supplyAsync(()->{
            try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }
            return 1;
        }), r ->{
            return r;
        }).join();
        // 哪个线程跑的最快用那个
        System.out.println(join);  // 1
    }

5.对计算结果进行合并

thenCombine对计算结果进行合并

    public static void main(String[] args) {
        Integer join = CompletableFuture.supplyAsync(() -> {
            return 10;
        }).thenCombine(CompletableFuture.supplyAsync(() -> {
            return 20;
        }), (r1, r2) -> {
            return r1 + r2;
        }).join();
        System.out.println(join);  // 30
    }

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