ForkJoin 案例

簡介

ForkJoin 通俗來講就是把一件事情拆分成若干個遞歸的小事情，並且框架提供多線程形式併發完成多個小事情後合併結果，完成大事情

小代碼實例

/**
 * 測試客戶端
 *
 * @author ljs.song
 * @date 2017-11-07 17:50
 */
public class Test {

    public static void main(String[] args) throws Exception {

        ForkJoinPool forkJoinPool = new ForkJoinPool();
        LongAdder sum = new LongAdder();
        List<Integer> nums = Arrays.asList(1,2,3,4,5,6,7,8,9);
        forkJoinPool.invoke(new AddTask(nums,sum));
        forkJoinPool.shutdown();
        System.out.println(sum);
    }

    

    private static class AddTask extends RecursiveAction{

        private List<Integer> nums;
        private LongAdder sum;

        public AddTask(final List<Integer> nums, LongAdder sum) {
            this.nums = nums;
            this.sum = sum;
        }

        /**
         * 拆分任務，二分法拆分數組，拆到只有一個元素後再分別累加
         */
        @Override
        protected void compute() {
            System.out.println(Thread.currentThread().getName());
            int size = nums.size();
            if(size > 1){
                int parts = size /2;
                List<Integer> left = nums.subList(0, parts);
                AddTask leftTask = new AddTask(left, sum);
                List<Integer> right = nums.subList(parts,size);
                AddTask rightTask = new AddTask(right, sum);
                invokeAll(leftTask, rightTask);
            }else{
                if(size == 0){
                    return ;
                }
                sum.add(nums.get(0));
            }
        }
    }
}