有效括号

20. 有效的括号

 public static boolean isValid(String s) {
        if (StringUtils.isEmpty(s)) {
            return false;
        }
        char[] chars = s.toCharArray();
        Stack<Character> stack = new Stack<Character>();
        for (char c : chars) {
            if (stack.isEmpty()) {
                stack.push(c);
            }else {
                if (match(stack.peek(), c)) {
                    stack.pop();
                } else {
                    stack.push(c);
                }
            }
        }
        return stack.isEmpty();
    }
    private static boolean match(char a, char b) {
        if (a == '[' && b == ']') {
            return true;
        }
        if (a == '(' && b == ')') {
            return true;
        }
        if (a == '{' && b == '}') {
            return true;
        }
        return false;
    }