这段Fork/Join排序为什么在递归了几步后就停止了，输出并没有排序完成。

class MergerSort extends RecursiveAction {
    private int[] array;
    private int begin, end, threshold;
    protected MergerSort(int[] array, int begin, int end, int threshold) {
        this.array = array;
        this.begin = begin;
        this.end = end;
        this.threshold = threshold;
    }
    private void merger(int begin, int mid, int end) {
        int i = begin, j = mid + 1, k = 0;
        int[] temp = new int[end - begin + 1];
        while (i <= mid && j <= end) {
            if(array[i] < array[j])
                temp[k++] = array[i++];
            else
                temp[k++] = array[j++];
        }
        while(i <= mid)
            temp[k++] = array[i++];
        while(j <= end)
            temp[k++] = array[j++];
        while(--k >= 0)
            array[end--] = temp[k];
    }
    @Override
    protected void compute() {
        if (end - begin < threshold) {
            //小于阈值，使用一般排序算法
            Arrays.sort(array, begin, end + 1);
        } else {
            //使用并发归并排序
            int mid = (end - begin) / 2;
            MergerSort left = new MergerSort(array, begin, mid, threshold);
            MergerSort right = new MergerSort(array, mid + 1, end, threshold);
            left.fork();
            right.fork();
            left.join();
            right.join();
            merger(begin, mid, end);
        }
    }
}

输出：
1 1 2 2 6 7 23 23 52 56 58 8 5 4 9 4 6 4 1 8 4 14 5 798 4 56 153 321 7 56 0 3 456 23 1 65 3 454 8 63 78

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不知道你其他部分什么样子
不过一眼看去int mid = (end - begin) / 2;明显应该是int mid = (end + begin) / 2;