Array-> Contains duplicate[Using Hasmap]

import java.util.*;
class Main {
    public static boolean containsDuplicate(int[] nums) {
        HashMap<Integer,Integer> map = new HashMap();
        for(int i=0;i<nums.length;i++){
            if(map.containsKey(nums[i])){
               return true; 
            }
            else{
                map.put(nums[i],i);
            }
        }
        return false;
    }

    public static void main(String[] args) {
        int nums[]={1,2,3,1};
        System.out.println(containsDuplicate(nums));
    }
}