打乱数组问题

class Solution {
    private final int[] nums;
    private final int[] shuffle;
    private final Random random;
    public Solution(int[] nums) {
        this.nums = nums;
        this.random = new Random();
        this.shuffle = Arrays.copyOf(nums, nums.length);
    }
    public int[] reset() {
        return nums;
    }
    public int[] shuffle() {
        for (int i = shuffle.length - 1; i >= 0; --i) {
            int n = random.nextInt(i + 1);
            int t = shuffle[i];
            shuffle[i] = shuffle[n];
            shuffle[n] = t;
        }
        return shuffle;
    }
}