Remove Duplicates from Sorted Array (LeetCode Array)

Question: Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.
Do not allocate extra space for another array, you must do this in place with constant memory.
For example,
Given input array A = [1,1,2],
Your function should return length = 2, and A is now [1,2].

Idea: Use two pointers i, j. i points to the last unique number, use j to scan the array from left to right. Since this is a sorted array, whenever num[j]!=num[i], it indicates a new unique number. We increase i by 1 and copy num[j] to the new position i pointing at, then continue increasing j. When j finishes scanning all the numbers, return the result.

Time: O(n) Space: O(1)

Code:

 public class Solution {  
   public int removeDuplicates(int[] A) {  
     if(A==null||A.length==0)  
       return 0;  
     int i=0;  
     for(int j=i+1;j<A.length;j++)  
     {  
       if(A[i]!=A[j])  
         A[++i]=A[j];  
     }  
     return i+1;  
   }  
 }