示例

计算一组数据，设置阈值为50，也就是说每次计算的数量不超过50个。

public class RecursiveTaskDemo extends RecursiveTask<Integer> {    private static final int MAX = 50;    private int[] arr;    private int start;    private int end;    public RecursiveTaskDemo(int[] arr, int start, int end) {        this.arr = arr;        this.start = start;        this.end = end;    }    @Override    protected Integer compute() {        if ((end - start) < MAX) {            int sum = 0;            for (int i = start; i <= end; i++) {                sum += arr[i];            }            return sum;        } else {            int mid = (end + start) / 2;            RecursiveTaskDemo left = new RecursiveTaskDemo(arr, start, mid);            RecursiveTaskDemo right = new RecursiveTaskDemo(arr, mid + 1, end);            invokeAll(left, right);            return left.join() + right.join();        }    }    public static void main(String[] args) {        ForkJoinPool pool = new ForkJoinPool();        int[] randomArr = getRandomArr(1000);        RecursiveTaskDemo task = new RecursiveTaskDemo(randomArr, 0, randomArr.length - 1);        System.out.println("总数1=" + pool.invoke(task));        System.out.println("总数2=" + Arrays.stream(randomArr).parallel().sum());    }    public static int[] getRandomArr(int num) {        int[] arr = new int[num];        for (int i = 0; i < arr.length; i++) {            arr[i] = new Random().nextInt(1000);        }        return arr;    }}

运行结果如下：

可以看出，两次结果是一样的。

步骤

1. 创建ForkJoinPool对象。
2. 创建继承RecursiveTask的类，实现compute方法，这里主要是计算以及拆分任务、合并结果。
3. pool.invoke方法调用。