217.存在重复元素

class Solution {
    public boolean containsDuplicate(int[] nums) {
        Set<Integer> hashSet = new HashSet<>();
        for(int i = 0;i<nums.length;i++){
            if(hashSet.contains(nums[i])){
                return true;
            }
            hashSet.add(nums[i]);
        }
        return false;
    }
}