原题链接: https://oj.leetcode.com/problems/valid-parentheses/

public boolean isValid(String s) {
    if (s == null) return false;

    int length = s.length();
    char c;
    Stack<Character> stack = new Stack<Character>();

    for (int i = 0; i < length; i++) {
        c = s.charAt(i);

        switch (c) {
            case '(':
            case '{':
            case '[':
                stack.push(c);

                break;

            case ')':
                try {
                    char prevChar = stack.pop();
                    if (prevChar != '(') return false;  
                } catch (Exception e) {
                    return false;
                }

                break;

            case '}':
                try {
                    char prevChar = stack.pop();
                    if (prevChar != '{') return false;  
                } catch (Exception e) {
                    return false;
                }

                break;

            case ']':
                try {
                    char prevChar = stack.pop();
                    if (prevChar != '[') return false;  
                } catch (Exception e) {
                    return false;
                }

                break;

            default:
                return false;
        }
    }

    if (!stack.isEmpty()) return false;

    return true;
}