Program: 19066
Project: 19066
Buggy source:
public void onEvent(JoinEvent event){
  String username=event.getUser();
  String ip=event.getIP();
  MCBouncer controller=event.getController();
  try {
    PlayerUpdateEvent updateEvent=new PlayerUpdateEvent(username,ip);
    MCBEventHandler.callEvent(updateEvent);
    if (updateEvent.isCancelled()) {
      return;
    }
    username=updateEvent.getUsername();
    ip=updateEvent.getIP();
    controller.getAPI().updateUser(username,ip);
    if (controller.getAPI().isBanned(username)) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str" + controller.getAPI().getBanReason(username));
      controller.getLogger().info(username + "String_Node_Str" + ip);
      return;
    }
    if (controller.getAPI().isIPBanned(ip)) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str" + controller.getAPI().getIPBanReason(ip));
      controller.getLogger().info(username + "String_Node_Str" + ip);
      return;
    }
    int numBans=controller.getAPI().getTotalBanCount(username,ip);
    int numNotes=controller.getAPI().getNoteCount(username);
    if (controller.getConfiguration().getNumBansDisallow() > 0 && numBans > controller.getConfiguration().getNumBansDisallow()) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str");
      controller.getLogger().info(username + "String_Node_Str" + numBans+ "String_Node_Str");
      return;
    }
    if (numBans > 0 || numNotes > 0) {
      String response=username + "String_Node_Str";
      if (numNotes == 0) {
        response+=numBans + "String_Node_Str" + (numBans == 1 ? "String_Node_Str" : "String_Node_Str");
      }
 else       if (numBans == 0) {
        response+=numNotes + "String_Node_Str" + (numNotes == 1 ? "String_Node_Str" : "String_Node_Str");
      }
 else {
        response+=numBans + "String_Node_Str" + (numBans == 1 ? "String_Node_Str" : "String_Node_Str")+ "String_Node_Str"+ numNotes+ "String_Node_Str"+ (numNotes == 1 ? "String_Node_Str" : "String_Node_Str");
      }
      controller.getServer().messageMods(ChatColor.GREEN + response);
    }
  }
 catch (  NetworkException ne) {
    controller.getLogger().severe("String_Node_Str",ne);
  }
catch (  APIException ae) {
    controller.getLogger().severe("String_Node_Str",ae);
  }
  controller.getCurrentlyLoggingIn().remove(username);
  controller.getServer().broadcastMessage(event.getMessage());
}

Fixed version (ground truth):
public void onEvent(JoinEvent event){
  String username=event.getUser();
  String ip=event.getIP();
  MCBouncer controller=event.getController();
  try {
    PlayerUpdateEvent updateEvent=new PlayerUpdateEvent(username,ip);
    MCBEventHandler.callEvent(updateEvent);
    if (updateEvent.isCancelled()) {
      return;
    }
    username=updateEvent.getUsername();
    ip=updateEvent.getIP();
    if (!controller.getConfiguration().isIPFunctionsDisabled()) {
      controller.getAPI().updateUser(username,ip);
    }
    if (controller.getAPI().isBanned(username)) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str" + controller.getAPI().getBanReason(username));
      controller.getLogger().info(username + "String_Node_Str" + ip);
      return;
    }
    if (!controller.getConfiguration().isIPFunctionsDisabled() && controller.getAPI().isIPBanned(ip)) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str" + controller.getAPI().getIPBanReason(ip));
      controller.getLogger().info(username + "String_Node_Str" + ip);
      return;
    }
    int numBans=controller.getAPI().getTotalBanCount(username,ip);
    int numNotes=controller.getAPI().getNoteCount(username);
    if (controller.getConfiguration().getNumBansDisallow() > 0 && numBans > controller.getConfiguration().getNumBansDisallow()) {
      controller.setLastKickedUser(username);
      controller.getCurrentlyLoggingIn().remove(username);
      controller.getServer().kickPlayer(username,"String_Node_Str");
      controller.getLogger().info(username + "String_Node_Str" + numBans+ "String_Node_Str");
      return;
    }
    if (numBans > 0 || numNotes > 0) {
      String response=username + "String_Node_Str";
      if (numNotes == 0) {
        response+=numBans + "String_Node_Str" + (numBans == 1 ? "String_Node_Str" : "String_Node_Str");
      }
 else       if (numBans == 0) {
        response+=numNotes + "String_Node_Str" + (numNotes == 1 ? "String_Node_Str" : "String_Node_Str");
      }
 else {
        response+=numBans + "String_Node_Str" + (numBans == 1 ? "String_Node_Str" : "String_Node_Str")+ "String_Node_Str"+ numNotes+ "String_Node_Str"+ (numNotes == 1 ? "String_Node_Str" : "String_Node_Str");
      }
      controller.getServer().messageMods(ChatColor.GREEN + response);
    }
  }
 catch (  NetworkException ne) {
    controller.getLogger().severe("String_Node_Str",ne);
  }
catch (  APIException ae) {
    controller.getLogger().severe("String_Node_Str",ae);
  }
  controller.getCurrentlyLoggingIn().remove(username);
  controller.getServer().broadcastMessage(event.getMessage());
}