栈应用——最长括号匹配

/**
     * 给定一个字符串，返回字符串中括号的最大匹配长度
     * @param s
     * @return
     */
    public int getLongestParenthese(String s) {
        char[] ch = s.toCharArray();
        Stack<Integer> stack = new Stack<Integer>();
        int start = -1;
        int max = 0;
        for(int i=0; i<ch.length; i++) {
            if(ch[i] == ‘(‘)
                stack.push(i);
            else {
                if(stack.isEmpty()) 
                    start = i;
                else {
                    stack.pop();
                    if(stack.isEmpty()) 
                        max = Math.max(max, i-start);
                    else 
                        max = Math.max(max, i-stack.peek());
                }
            }
        }
        return max;
    }