CompletableFuture

Posted 2020-11-22 moris5013

public class CompletableFutureTest {

    public static void main(String[] args) throws Exception {
//        test2();
//        test1();
//        test3();
        test4();
    }


    //采用了callable+ future方式
    public  static  void  test1() throws  Exception {
        ExecutorService executor = Executors.newCachedThreadPool();
        Future<String> result = executor.submit(()->{
            //模拟执行耗时任务
            System.out.println("task doing...");
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            //返回结果
            return "result";
        });
        //这里只是将空闲的线程中断，将线程池的状态改为shutdown,不能继续往线程池中添加任务
        executor.shutdown();
        System.out.println("task运行结果" + result.get());
    }


    //采用了competableFuture方式
    public static void test2() throws Exception {
        //supplyAsync内部使用ForkJoinPool线程池执行任务
        CompletableFuture<String> completableFuture=CompletableFuture.supplyAsync(()->{
            //模拟执行耗时任务
            System.out.println("task doing...");
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            //返回结果
            return "result";
        });
        System.out.println("计算结果:"+completableFuture.get());
    }

    public static void test3() throws Exception {
        CompletableFuture<Integer> completableFuture = new CompletableFuture<>();
        new Thread(() -> {
            System.out.println("task doing...");
            try {
                Thread.sleep(5_000);
//                int  i = 1/0;
                completableFuture.complete(10);//如果价格计算正常结束，完成Future操作并设置商品价格
            } catch (Exception ex) {
                completableFuture.completeExceptionally(ex);//否则抛出导致失败的异常，完成这次Future操作
            }
        }).start();
        System.out.println("计算结果:"+completableFuture.get());
    }


    //一个线程计算奇数和，一个线程计算偶数和，main线程将他们相加
    public static  void test4() throws ExecutionException, InterruptedException {

        CompletableFuture<Integer> oddNumber = CompletableFuture.supplyAsync(()->{
            try {
                System.out.println("开始计算奇数和  ...");
                Thread.sleep(3_000);
                System.out.println("结束计算奇数和  ...");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return   1+3+5+7+9;
        });
        CompletableFuture<Integer> evenNumber = CompletableFuture.supplyAsync(()->{
            try {
                System.out.println("开始计算偶数和  ...");
                Thread.sleep(5_000);
                System.out.println("结束计算偶数和  ...");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return 2+4+6+8;
        });
        long startTime = System.currentTimeMillis();
        CompletableFuture<Integer> resultFuturn = oddNumber.thenCombine(evenNumber,(odd,even)->{
            return odd + even;
        });
        System.out.println("===============");
        System.out.println("运行结果是："+resultFuturn.get()+" 总共耗时："+ (System.currentTimeMillis()-startTime) +"毫秒");
    }

}