Minimum Add to Make Parentheses Valid.java

https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/
class Solution {
    public int minAddToMakeValid(String s) {
        Stack<Character> st = new Stack<>();
            for(int i = 0;i<s.length();i++){
                if(st.size()>0 && st.peek() == '(' && s.charAt(i) == ')'){
                    st.pop();
                }
                else{
                    st.push(s.charAt(i));
                }
            }
        return st.size();
        }   
    }