LeetCode 219--- Contains Duplicate II

public class Problem219 {

public static void main(String[] args) {
// TODO Auto-generated method stub

}
public boolean containsNearbyDuplicate(int[] nums, int k) {
HashMap<Integer,Integer> hashtable = new HashMap<Integer,Integer>();

for(int i = 0; i < nums.length; i++){
if(hashtable.containsKey(nums[i]) && i - hashtable.get(nums[i]) <=k){
return true;
}
hashtable.put(nums[i],i);
}

return false;
}

}