为什么快速选择这么慢？

问：

    public void findKthLargest(int[] nums, int k) {

        // quick select for quickSelect1
        quickSelect1(nums, 0, nums.length -1, nums.length - k);
        
        // quick select for quickSelect2
        quickSelect2(nums, 0, nums.length -1, k-1);

    }
    int quickSelect1(int[] nums, int l, int r, int k) {
        if (l == r) return nums[k];
        int x = nums[l], i = l - 1, j = r + 1;
        while (i < j) {
            do i++; while (nums[i] < x);
            do j--; while (nums[j] > x);
            if (i < j){
                int tmp = nums[i];
                nums[i] = nums[j];
                nums[j] = tmp;
            }
        }
        if (k <= j) return quickSelect1(nums, l, j, k);
        else return quickSelect1(nums, j + 1, r, k);
    }

    private int quickSelect2(int[] nums, int left, int right, int k) {

        if(left >= right)
            return nums[k];

        int p = new Random().nextInt(right - left + 1) +  left;
        int pp = nums[p];
        swap(nums, p, left);

        int i = left + 1;
        int j = right;

        while (true) {

            while (i <= j && nums[i] >= pp) {
                i++;
            }
            while (j >= i && nums[j] < pp) {
                j--;
            }

            if(i > j)
                break;

            int tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
            i++;
            j--;
        }

        if(j != left)
            swap(nums, j, left);

        if(j == k)
            return pp;
        else if(j > k){
            return quickSelect2(nums, left, j - 1, k);
        }else{
            return quickSelect2(nums, j + 1, right, k);
        }
    }

    private void swap(int[] nums, int index1, int index2) {
        int temp = nums[index1];
        nums[index1] = nums[index2];
        nums[index2] = temp;
    }

那为什么这么慢呢？quickSelect2quickSelect1