384. Shuffle an Array

Q:

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();

A:

***********首先要有个nums的备份， 然后每次返回的时候，要一个shuffle的备份 *******

public class Solution {
    private static int[] A;
    private int[] B;
    public Solution(int[] nums) {
        A = nums;
        B = new int[A.length];
        for(int i = 0;i<A.length;i++)
            B[i] = A[i];
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        for(int i = 0;i<A.length;i++)
            B[i] = A[i];
        return B;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        for(int i =B.length-1;i>0;i--){
            int j = (int)(Math.random()*(i+1));
            int tmp = B[i];
            B[i] = B[j];
            B[j] = tmp;
        }
        return B;
    }
}

/**
 * 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();
 */ 

Errors: