java 任務分解

使用  java.util.concurrent.Callable 

 

public static void main(String[] args){

        FutureTask<Integer> task = new FutureTask<>(new MyTask());

        task.run();

        try {
            task.get();  //這裏是阻塞的，直到 mytask運行完成
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

    }

   static class MyTask implements Callable<Integer>{

        /**
         Computes a result, or throws an exception if unable to do so.
         @return computed result
         @throws Exception if unable to compute a result
         */
        @Override
        public Integer call() throws Exception {
             System.out.println("start");
            return 1;
        }
    }

咱們線程經常使用的是繼承 Runable 。這是沒有返回值的。可是Callable  有返回值，並且有異常拋出

 

使用 java.util.concurrent.ForkJoinTask

 

public static void main(String[] args) throws ExecutionException, InterruptedException {

        System.out.println("-----------main being---------------");
        ForkJoinPool forkJoinPool = new ForkJoinPool();

        MyTask myTask = new MyTask("mainTask");
        forkJoinPool.submit(myTask);


        System.out.println(myTask.get());
        System.out.println("-----------main end---------------");
    }

    static class MyTask extends RecursiveTask<Integer> {
        private String name;

        public MyTask(String name) {
            this.name = name;
        }

        /**
         The main computation performed by this task.
         @return the result of the computation
         */
        @Override
        protected Integer compute() {

            if ("leftTask".equals(name) || "rightTask".equals(name)) {
                System.out.println("begin:  【" + name + "】");
                try {
                    Thread.sleep(2000L);
                } catch (InterruptedException e) {
                    //
                }
                System.out.println("end:  【" + name + "】");
                return 1;
            }

            MyTask leftTask = null;
            MyTask rightTask = null;
            if ("mainTask".equals(name)) {
                System.out.println("begin:  【" + name + "】");

                leftTask = new MyTask("leftTask");
                rightTask = new MyTask("rightTask");

                leftTask.fork();
                rightTask.fork();
                System.out.println("end:  【" + name + "】");
            }


            return rightTask.join() + leftTask.join();
        }

 

RecursiveTask 是有返回值的， RecursiveAction 是沒有返回值的