提取中括号中的内容

/**
     * 提取中括号中内容
     * @param msg
     * @return
     */
    public static List<String> extractMessage(String msg) {

        List<String> list = new ArrayList<String>();
        int start = 0;
        int startFlag = 0;
        int endFlag = 0;
        for (int i = 0; i < msg.length(); i++) {
            if (msg.charAt(i) == '[') {
                startFlag++;
                if (startFlag == endFlag + 1) {
                    start = i;
                }
            } else if (msg.charAt(i) == ']') {
                endFlag++;
                if (endFlag == startFlag) {
                    list.add(msg.substring(start + 1, i));
                }
            }
        }
        return list;
    }