Contains Duplicate II

import java.util.Hashtable;public class Solution {    public boolean containsNearbyDuplicate(int[] nums, int k) {        Hashtable<Integer, Integer> intToIntHashtable = new Hashtable<Integer, Integer>();        for(int i = 0; i < nums.length; ++i) {            if(intToIntHashtable.containsKey(nums[i]) && i - intToIntHashtable.get(nums[i]) <= k) {                return true;            }else {                intToIntHashtable.put(nums[i], i);            }        }        return false;    }}