add player to list, oop.

Hey i want to create arenamanager, and i had problem in add player to arraylist in arena.

I'm using that function:

Code:java

    private ArrayList<Player> players;
 
    public void AddPlayer(Player p){
        players.add(p);
    }

then i add with this:

Arena a = ArenaManager.getArena(1);
a.AddPlayer(e.getPlayer());

And im sure that arena exists

But when i wan to add this player finaly:

Code:

org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:294) ~[Craftbukkit.jar:git-Craftbukkit-1387]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[Craftbukkit.jar:git-Craftbukkit-1387]
    at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:30) ~[Craftbukkit.jar:git-Craftbukkit-1387]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [Craftbukkit.jar:git-Craftbukkit-1387]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.PlayerList.c(PlayerList.java:249) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.PlayerList.a(PlayerList.java:135) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.LoginListener.c(LoginListener.java:97) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.LoginListener.a(LoginListener.java:42) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.NetworkManager.a(NetworkManager.java:151) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.ServerConnection.c(ServerConnection.java:77) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.MinecraftServer.v(MinecraftServer.java:705) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.DedicatedServer.v(DedicatedServer.java:273) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.MinecraftServer.u(MinecraftServer.java:568) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.MinecraftServer.run(MinecraftServer.java:474) [Craftbukkit.jar:git-Craftbukkit-1387]
    at net.minecraft.server.v1_7_R2.ThreadServerApplication.run(SourceFile:618) [Craftbukkit.jar:git-Craftbukkit-1387]
Caused by: java.lang.NullPointerException
    at pl.diverse.mercenaryDeathmatch.Managers.Arena.AddPlayer(Arena.java:28) ~[?:?]
    at pl.diverse.mercenaryDeathmatch.Listeners.Join.onJoin(Join.java:17) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_51]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_51]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_51]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_51]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:292) ~[Craftbukkit.jar:git-Craftbukkit-1387]
    ... 15 more

I dont know what is bad ;/ Can someone help me?

 

You need to initialize your ArrayList. I hope you continue learning Java first as it will make these problems more easy to avoid and solve.

 

human learns from his mistakes

Can yyou help me with this? I'm really fresh ;/

 

DevManABCD like teej107 said, you need to initialize your ArrayList. If you are incapable of doing so, then you are currently incapable of creating a Bukkit plugin.

 

I did mistake in loading configurationsection to arena, sorry for problem.

 

Try this its could help you very well this is my method

public List<String> redteam = new ArrayList<String>();
if(label.equalsIgnoreCase("red")) {
if(redteam.contains(p.getName())) {
redteam.add(p.getName());
p.sendMessage("You have joined the red Team");
}

}

 

DevManABCD
ProStriker123
Due to current changes in how players are identified, it is recommended that you save the UUID of the
player instead of the players name. Generally speaking, this is only necessary for when identifying a individual
player more than once, but it is good practise.
Try something along these lines:

Code:

/* You may want to change the first "String" to "Long" for the capturing of player's UUID
public HashMap<String,String> redTeam = new HashMap<>();
if(/*player opts for red team*/){
if(/*player not in team - not in HashMap*/){
/* if you setup HashMap as <String,String> use method 1, if you setup as <Long,String> use method 2*/
//method 1
redTeam.put(player.getUniqueId().toString(),player.getName());
//method 2
redTeam.put(player.getUniquId(),player.getName());
/*only use one of the methods*/
}
}

Note 1: This code is untested and may contain errors/bugs
Note 2: In this code example I saved players name alongside UUID

Hope this helped!

- Minty

 

TheMintyMate Assuming he removes them on PlayerQuitEvent, it is perfectly fine to use names. They are perfectly fine for session storage, and you only need to go to UUIDs if you want to extend beyond the session (not removing onQuit, or saving data)

 

Please note what I said in my post:
" but it is good practise."