/**
 * https://leetcode.com/problems/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.
 */
public class Solution {
	public boolean containsDuplicate(int[] nums) {
		if (nums.length == 0)
			return false;

		HashSet<Integer> set = new HashSet();
		for(int element : nums)
			set.add(element);

		return !(set.size() == nums.length);
	}
}

Create 217_Contains_Duplicate.java