The tricky part is that the relative order of non-zero values need to be maintained. A straightforward solution:

• traverse the array to find any non-zero value
• move the found value from step 1 to the front of the array using a pointer to keep track of index
• change all the values to zero after the pointer

    public static void moveZeroes2(int[] nums) {
        if (nums == null || nums.length < 2) return;
        int index = 0;
        for (int num : nums){
            if (num != 0){
                nums[index++] = num;
            }
        }
        for (; index < nums.length; index++){
            nums[index] = 0;
        }
        return;
    }