NullPointerException when checking ArrayList size

Hello,

My ArrayList is in another class, i'm if the size of the arraylist is a specific number. When I do this I get a NullPointerException. I created an instance of the class, i'm not sure if this is the correct way to do it.

This is the bit of my code that checks the ArrayList: http://pastebin.com/gn71WYmd

And i'm not sure if this is correct but: http://pastebin.com/KpEJ24UJ

One is for my main class and one is for the class containing the ArrayList

 

What does your arena class look like? Maybe you forgot to initialize your Player list when creating a new arena object?

 

import java.util.ArrayList;

public class PvPPluginArena {

public ArrayList<String> players = new ArrayList<String>();

public ArrayList<String> blue = new ArrayList<String>();

public ArrayList<String> red = new ArrayList<String>();



}

That's all I got currently

 

KungFuGoat Can you show where you initialize the "arenaClass" variable?

 

I don't think I have :C
How would I do that?

 

KungFuGoat Depends, what is your "arenaClass" variable? Can you show where you declare it?

 

In the PvPPluginManager class

 

You have 2 different Constructors for your PvPPluginManager-Class. One takes a plugin, the other one the PvPArenaClass. I'm assuming you create the manager with the constructor taking the plugin - hence the instance variable "arenaClass" is never assigned a value. That's why it's giving you a nullpointer when you try to use it.

 

KungFuGoat Like minoneer said, since you have 2 constructors for your PvPPluginManager class, there is a chance the one that defined the PvpPluginArena is never called. Instead of using 2 constructors, pass in both variables through a single constructor, allowing use of both without the chance of them not being declared like you currently have setup

 

How would I use the ArrayList in the manager class then?

 

The exact same way you are doing now.

Your current code:

Code:java

 
 
            public PvPPluginArena arenaClass;
 
            public PvPPluginManager(PvPPluginArena arenaClass){
 
                    this.arenaClass = arenaClass;
 
            }
 
            public PvPPlugin plugin;
 
            public PvPPluginManager(PvPPlugin plugin){
 
                    this.plugin = plugin;
 
            }
 
 

What you should do:

Code:java

 
 
            public PvPPlugin plugin;
            public PvPPluginArena arenaClass;
 
            public PvPPluginManager(PvPPluginArena arenaClass,  PvPPlugin plugin) {
                    this.plugin = plugin;
                    this.arenaClass = arenaClass;
 
            }
 
 

 

Thank you I appreciate it

One more thing, how would I register this then?

PvPPluginManager ppm = new PvPPluginManager(this);
this.getServer().getPluginManager().registerEvents(ppm, this);
this.getCommand("setarena").setExecutor(ppm);

This is what I had before, but now eclipse is giving me a The constructor PvPPluginManager(PvPPlugin) is undefined

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Of course it is, since you aren't passing all required arguments. If you don't know what I'm talking about, you should consider taking a stepp back, look into learning how Java method calls and constructors work, and then come back and fix it I won't explain basic java or give you ready to use code.

 

Well, i was sort of trying to learn as I go along

 

You should know the baiscs first. Once you do, that's perfectly fine.

 

I figured it out Thanks for the help

 

Great! Good job