Fetching list by UUID turns out null

Hello Bukkit Developers! I have a problem and I don't know why it is happening. Let's walk through it.

First we will start with the code which can be located here: http://pastebin.com/Z8pxZ0F1

Second, the problem.
When a player is added to a hitlist, the plugin gets the UUIDs of both players, adds the uuid of the person being added to a list that will be put into a hashmap. Then the hashmap is updated with the new information. I am trying to get the list and send it in a message to a player (the player checking who is on their list). When I do so, the list returns null.

** NOTE **
I HAVE CHECKED IF THE LIST IS NULL, I JUST REMOVED IT FOR NOW!

I'm not sure why the list is returning back null and I have checked my code multiple times. Thank you for any help you may be able to contribute in advance!

 

excusemyluck

First, when you add or remove a UUID from the list, you check if this list is null OR doesn't contain the player to be added. If it isn't null and doesn't contain the player, it creates a new List (thus, any other players stored in the list will be removed and the list will only ever contain one UUID.)

Second, you don't need to remove the entry from the map to store it with the updated list, just use .put again, it will replace the current value associated to the key (no duplicate entries within a HashMap.)

Third, you should initialize your fields within a constructor. I see no reason to initialize the HashMap within the class body unless it's constant (static final), which you would not need in this situation. As Garris0n pointed out, your prefix does appear to be constant, so you could make it public static final.

Finally, you could do something like this:

Code:java

hitlistMap = new HashMap<UUID, List<UUID>>();
 
//In your add method:
 
if (!hitlistMap.containsKey(uuidOfAdding))
    hitlistMap.put(uuidOfAdding, new ArrayList<UUID>());
 
hitlistMap.get(uuidOfadding).add(uuidOfAdded);
 
//In your remove method:
 
if (hitlistMap.containsKey(uuidOfRemoving)){
    if (hitlistMap.get(uuidOfRemoving).contains(uuidOfRemoved))
        hitlistMap.get(uuidOfRemoving).remove(uuidOfRemoved);
}

 

I can only assume it's because you haven't added the list to the map...

Actually, that prefix looks to actually be a constant, so it should in fact be static and final (and renamed in all caps with words separated by underscores).

 

Garris0n

Thanks for spotting that

 

Dragonphase Noting your edit, it wouldn't have to be public for any reason if it's only in that class.

 

Garris0n

True, force of habit and assuming he'd be using the prefix elsewhere in his project

 

Dragonphase Garris0n
I made the edits that both of you said should be made, but my list is still returning null. Is there anything I'm really missing here that I should be doing? And thank you both for the help!

 

excusemyluck

Out of interest, where are you calling your methods from? Do you create multiple instances of HitlistManager whenever you attempt to issue one of those methods?

 

Post the edited code, and include all relevant code this time (i.e. the part you're testing with as well).

 

Garris0n Dragonphase I'm calling the methods from my command classes. Any no, I just call the methods which handle all of the work (the methods in the class below).

Updated Class: http://pastebin.com/hdLhMH7N
Base Command Class: http://pastebin.com/Fb2PfFfy
List Command Class (used the same way as my add/remove commands): http://pastebin.com/xgfcRpcx

Once again, thank you both for the taking the time to help!

 

So where are you calling the method that adds the list to the map?

 

That would be my add command. I don't want to flood you with another class, but here is the section of code that calls the add method:

Code:java

if (args.length == 2) {
hlm.addToHitlist(player, Bukkit.getServer().getPlayer(args[1]));
} else {
player.sendMessage(phl.prefix + ChatColor.RED + "Usage: /phl add <username>");
}

 

That was pretty much exactly what I meant, actually

 

I had the feeling that I was doing that. Sorry if it's annoying, at this point I'll give you the relevant code, like you asked for earlier.

 

excusemyluck

In your C_List.java class, where you are calling hlm.listPlayersOnHitlist(player):

Code:java

private HitlistManager hlm = new HitlistManager();

hlm is a new instance. You should create one instance of it, in your plugin for example, and use plugin.getHitlistManager()

 

No, what I meant was you should just post all relevant code (as in the entire classes)

I should've worded that response better.

I'm already fairly sure I know what the problem is, I just figure it's best to make sure, which requires that other command's class.

 

After my permission and argument checks:

Code:java

if (args.length == 1) {
hlm.listPlayersOnHitlist(player);
} else {
player.sendMessage(phl.prefix + ChatColor.RED + "Usage: /phl list");
}

What class do you need?

 

The class from what you just posted

I'm next to positive that Dragonphase is right, I just never say until I'm actually sure.

 

excusemyluck

You misunderstand me. The HitlistManager object within your C_List class is a new instance of HitlistManager. This means that any other instance of the HitlistManager you created and made changes to will not apply to the one within your C_List class.

Most people would get frustrated at this point, and create one static HitlistManager, which is bad.

Create one HitlistManager inside your plugin's main class, create a getter for it (getHitlistManager()), and use plugin.getHitlistManager() for anything related to modifying or retrieving data from HitlistManager.

 

http://pastebin.com/8byXiwfU
There you go

Something I haven't thought of and something I feel I will do!

 

That's the list class

Just make sure you're using the same instance as Dragonphase has been saying.

 

Well I just made that instance.

And sorry, here is the add command
http://pastebin.com/hi62HmT6

 

This is getting a bit ridiculous, but, uh...where are you instantiating that?

(and when I say where I mean the entire class)

 

You know I'm about to just upload this on github lol.

And I made the new instance in the main class (which I probably did wrong anyways, but I gave it a shot)...
http://pastebin.com/u8fbPtze

 

No, they have to have one single HitlistManager. Just one, never create another after that. So save an instance variable in the main class and, whenever you need a HitlistManager, use that getter (which you should modify to return the instance).

 

Garris0n
Okay thats an easy fix. And I'm uploading on github now to make this easier (which I'm sorry that I'm making this so hard )

 

excusemyluck

Your getter will return a new instance of a HitlistManager every time you invoke it. You need to create one instance of it, and return that one instance within your getter:

Code:java

private HitlistManager hitlistManager;
 
public void onEnable(){
    //code
    hitlistManager = new HitlistManager();
}
 
public HitlistManager getHitlistManager(){
    return hitlistManager;
}

Then, use phl.getHitlistManager(); whenever you need to retrieve it. (Assuming you pass your plugin to the constructors where you need to get the HitlistManager.)

 

Dragonphase Garris0n
OKAY, all fixed. The getter atleast. And instead of using pastebin and posting 50 more links, I uploaded it to github.
https://github.com/excusemyluck/PlayerHitlist/blob/master/src/me/eml/phl/PlayerHitlist.java

Also, Sorry for... well, this.

 

Well, does it work now?

 

Garris0n Dragonphase OH MY GOD THE TWO OF YOU ARE BEAUTIFUL MEN! Holy crap thank you.