20.Valid Parentheses

import java.util.HashMap;
import java.util.Map;
import java.util.Stack;

public class Solution {
public boolean isValid(String s) {
Stack<Character> characterStack = new Stack<>();
int len = s.length();
Map<Character, Character> map = new HashMap<>();
map.put(')', '(');
map.put(']', '[');
map.put('}', '{');
for(int i = 0; i < len; ++i) {
if( characterStack.isEmpty()) {
characterStack.push(s.charAt(i));
continue;
}
Character c = s.charAt(i);
Character t = characterStack.peek();
if(t == map.get(c)) characterStack.pop();
else characterStack.push(c);
}
return characterStack.isEmpty();
}
//
//    public static void main(String[] args) {
//        Solution solution = new Solution();
//        System.out.println(solution.isValid("()"));
//    }
}