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;
}
}