3-6

class Solution {
    public void moveZeroes(int[] nums) {
        if (nums == null || nums.length == 0) {
            return;
        }

        // Insert non-zero values at the beginning
        // of the array, one-by-one.
        int insertPosition = 0;
        for (int num: nums) {
            if (num != 0) {
                nums[insertPosition++] = num;
            }
        }

        // Fill the rest of the positions with 0.
        while (insertPosition < nums.length) {
            nums[insertPosition++] = 0;
        }
    }
}