leetcode-简单-栈-有效的括号

class Solution {
    public boolean isValid(String s) {
         int len = s.length();
        if(len == 0)    return true;

        Stack<Character> stack = new Stack<>();
        Map<Character,Character> map = new HashMap<Character, Character>(){
            {
                put(‘(‘,‘)‘);
                put(‘[‘,‘]‘);
                put(‘{‘,‘}‘);
            }
        };
        for(int i = 0; i < len; i++){

            if(map.containsKey(s.charAt(i))){
                stack.push(s.charAt(i));
            }else if(!stack.empty() && map.get(stack.peek()) == s.charAt(i)){
                stack.pop();
            }else{
                return false;
            }

        }

        return stack.empty();
    }
}