Contains Duplicate

public class Solution {
    public boolean containsDuplicate(int[] nums) {
        if(nums==null||nums.length==0) return false;
        Set<Integer> s = new HashSet<Integer>();
        for(int i=0;i<nums.length;i++){
            if(s.contains(nums[i])) {
                return true;
            }else
                s.add(nums[i]);
        }
        return false;
    }
}