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Future设计的初衷：对将来的某个事件的结果进行建模。

Future接口实现类CompletableFuture

image-20210325162332129

没有返回值的异步回调

public class Demo01 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        // 没有返回值的异步回调
        CompletableFuture<Void> completableFuture = CompletableFuture.runAsync(() -> {
            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+" runAsync==>void");
        });
        System.out.println("123456");
        // 阻塞,获取执行结果
        completableFuture.get();
    }
}

结果：

123455
ForkJoinPool.commonPool-worker-1 runAsync==>void
    
Process finished with exit code 0

有返回值的异步回调

正常执行

public class Demo01 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
         /**
         * 有返回值的异步回调
         * ajax 成功或者失败的回调
         */
        CompletableFuture<Integer> completableFuture = CompletableFuture.supplyAsync(() -> {
            System.out.println(Thread.currentThread().getName()+" supplyAsync==>Integer");
            return 1024;
        });
        Integer rst = completableFuture.whenComplete((t, u) -> {
            // 正常的返回结果
            System.out.println("t：" + t);
            System.out.println("u：" + u);
        }).exceptionally((e) -> {
            System.out.println(e.getMessage());
            return 233;
        }).get();
        System.out.println(rst);
    }
}

结果：

ForkJoinPool.commonPool-worker-1 supplyAsync==>Integer
t：1024
u：null
1024
    
Process finished with exit code 0

执行有异常

public class Demo01 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        /**
        * 有返回值的异步回调
        * ajax 成功或者失败的回调
        */
        CompletableFuture<Integer> completableFuture = CompletableFuture.supplyAsync(() -> {
            System.out.println(Thread.currentThread().getName()+" supplyAsync==>Integer");
            int i = 10 / 0;
            return 1024;
        });
        Integer rst = completableFuture.whenComplete((t, u) -> {
            // 正常的返回结果
            System.out.println("t：" + t);
            // 错误信息
            System.out.println("u：" + u);
        }).exceptionally((e) -> {
            System.out.println(e.getMessage());
            // 获取到错误的返回结果
            return 233;
        }).get();
        System.out.println(rst);
    }
}

结果：

ForkJoinPool.commonPool-worker-1 supplyAsync==>Integer
t：null
u：java.util.concurrent.CompletionException: java.lang.ArithmeticException: / by zero
java.lang.ArithmeticException: / by zero
233
    
Process finished with exit code 0