Leetcode: Move Zeroes

Given an array nums, write a function to move all 0‘s to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:
You must do this in-place without making a copy of the array.
Minimize the total number of operations.

 1 public class Solution {
 2     public void moveZeroes(int[] nums) {
 3         if (nums==null && nums.length==0) return;
 4         int l=0, r=0;
 5         while (l < nums.length && r < nums.length) {
 6             while (l<nums.length && nums[l]!=0) {
 7                 l++;
 8             }
 9             r = l;
10             while (r<nums.length && nums[r]==0) {
11                 r++;
12             }
13             if (l == nums.length || r == nums.length) break;
14             swap(nums, l, r);
15         }
16     }
17     
18     public void swap(int[] nums, int l, int r) {
19         int temp = nums[l];
20         nums[l] = nums[r];
21         nums[r] = temp;
22     }
23 }