有效的括号

public static boolean isValid(String s){
        Map<Character, Character> map = new HashMap<>();
        map.put('(',')');
        map.put('{','}');
        map.put('[',']');
        Stack stack = new Stack();
        for (char c : s.toCharArray()) {
            if (map.containsKey(c)){
                stack.push(c);
            }else {
                //如果不为null,且值相等则出栈
                if (!stack.isEmpty()&&map.get(stack.peek()).equals(c)){
                    stack.pop();
                }else {
                    return false;
                }
            }
        }
        //如果返回true的话，可能存在栈里面还有值的情况
        return stack.isEmpty();
    }