LeetCode-Shuffle an Array

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

Solution:

public class Solution {
    int[] numArr;

    public Solution(int[] nums) {
        numArr = new int[nums.length];
        for (int i=0;i<nums.length;i++){
            numArr[i] = nums[i];
        }
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        return numArr;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        int[] randArr = new int[numArr.length];
        for (int i=0;i<numArr.length;i++) randArr[i] = numArr[i];
        int last = numArr.length-1;
        Random engine = new Random();
        while (last>=0){
            int target = engine.nextInt(last+1);
            int temp = randArr[last];
            randArr[last] = randArr[target];
            randArr[target] = temp;
            last--;
        }
        return randArr;
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(nums);
 * int[] param_1 = obj.reset();
 * int[] param_2 = obj.shuffle();
 */