217. Contains Duplicate

Leetcode: 217. Contains Duplicate
Given an array of integers, find if the array contains any duplicates.
Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

Input: [1,2,3,1]
Output: true

Example 2:

Input: [1,2,3,4]
Output: false

Example 3:

Input: [1,1,1,3,3,4,3,2,4,2]
Output: true

Solution:

class Solution {
    public boolean containsDuplicate(int[] nums) {
        if(nums==null || nums.length == 0)
            return false;
        HashSet<Integer> set = new HashSet<>();
        for(int num: nums)
            if (!set.add(num)) // set will return boolean when call add function
                return true;
        return false;
    }
}