java正则获取字符串内容

public static void main(String[] args) {
    List<String> beanList = new ArrayList<>();
    String content = "{\"acsRequestBeanList\":[{\"mac\":\"00:0D:2D:34:84:40\",\"acsMethods\":[{\"method\":\"Reboot\",\"requestId\":\"1_1473473073377296386\",\"params\":null}]}]}";
    beanList.add(content);
    beanList.add(content);
    beanList.add(content);
    String pattern = "\\{\"acsRequestBeanList\"\\:\\[(.+)\\]\\}";
    Pattern p = Pattern.compile(pattern);
    StringBuffer builder = new StringBuffer();
    builder.append("{\"acsRequestBeanList\":[");
    for (String str : beanList) {
        Matcher m = p.matcher(str);
        if (m.find()) {
            String item = m.group(1);
            builder.append(item);
            builder.append(",");
        }
    }
    builder.append("]}");
}