private String urlEncode(String str) {
        return URLEncoder.encode(str, StandardCharsets.UTF_8);
    }
Get the members of the given group
@param groupName the name of the group
@return a List of String with the usernames members of the given group
@throws RemoteException if an exception occurred communicating with the crowd server
xmppserver/src/main/java/org/jivesoftware/openfire/crowd/CrowdManager.java