public ServerDatabase randomUser(Random random, ServerDatabase user) {
public DatabaseReference randomUser(Random random, ServerDatabase user) {
  public ServerDatabase randomUser(Random random, ServerDatabase user) {    if (users.size() == 0)       return null;     if (users.size() == 1 && users.elementAt(0) == user)      return null;        while (true) {      ServerDatabase peer = (ServerDatabase) users.elementAt((random.nextInt() & 0x7fffffff) % users.size());      if (peer != user)         return peer;    }  }