Solved NPE Giving me a headache

I am using a listener class and an API class (both separate from the main class) to do this. All I want to do is send a player into spectate mode when they die, but I am getting an NPE when I am calling my method.

Code:

@EventHandler
    public void onPlayerDeath(PlayerDeathEvent e){
       
        Player a =  e.getEntity();
       
        a.setHealth(20);
       
        api.setSpectating(a);
       
        if(a.getKiller() instanceof Player){
       
        e.setDeathMessage(ChatColor.DARK_RED + "Player " + ChatColor.GOLD + a.getName() + ChatColor.DARK_RED + " has fallen to " + ChatColor.GOLD + a.getKiller().getName());
       
        }
    }

That is my listener class, it works fine, the NPE is thrown at my method right here:

Code:

    public void setSpectating(Player p){

        if(p != null){
        if(spectating.size() < 10){
           
            plugin.chat.put(p.getName(), "spectate"); //NPE HERE
            p.sendMessage(plugin.tag + ChatColor.AQUA + "You are now spectating."); //NPE HERE IF LINE ABOVE IS REMOVED
            p.getInventory().clear();
           
            spectating.add(p.getName());
           
            p.setGameMode(GameMode.SPECTATOR);
        }else{
           
            for(Player s : Bukkit.getServer().getOnlinePlayers()){
                p.getInventory().clear();
                s.kickPlayer(ChatColor.DARK_RED + "Game over! " + ChatColor.GOLD + p.getName() + ChatColor.DARK_RED + " has won!");
                gameOver();
            }
        }
           
        }
       
    }

The odd thing is that it makes it past the null check-- I have a player, I just cant do anything with it.

I already tried initiating the variable, but that didn't work at all. NPE's suck.

Oh, and I reference my API class with the api.whatever

Code:

MortalAPI api = new MortalAPI(plugin);

 

@ColaCraft Possible that it's "plugin" that's null.

 

Code:

Main plugin;

    public MortalListener(Main plugin) {
        this.plugin = plugin;
    }

 

Why don't you give the stacktrace and the line of code the stacktrace points?

Also, just for the record Player#getKiller always returns a Player, so you can just check if it's null instead of checking instance.

 

instanceof does the same thing? I know I could do that.

Also, I have the line marked where the NPE is thrown, if you really want to read the stacktrace, here it is, it is just going to say the same thing

Code:

[18:22:23] [Server thread/INFO]: PorterK issued server command: /kill
[18:22:23] [Server thread/ERROR]: Could not pass event PlayerDeathEvent to MortalGames v1.0
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:297) ~[craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:501) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:486) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.craftbukkit.v1_8_R1.event.CraftEventFactory.callPlayerDeathEvent(CraftEventFactory.java:364) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.EntityPlayer.die(EntityPlayer.java:392) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.EntityLiving.damageEntity(EntityLiving.java:765) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.EntityHuman.damageEntity(EntityHuman.java:795) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.EntityPlayer.damageEntity(EntityPlayer.java:471) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.EntityLiving.G(EntityLiving.java:86) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.CommandKill.execute(SourceFile:29) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.craftbukkit.v1_8_R1.command.VanillaCommandWrapper.dispatchVanillaCommand(VanillaCommandWrapper.java:91) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.craftbukkit.v1_8_R1.command.VanillaCommandWrapper.execute(VanillaCommandWrapper.java:42) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:140) [craftbukkit.jar:git-Bukkit-f233e7d]
    at org.bukkit.craftbukkit.v1_8_R1.CraftServer.dispatchCommand(CraftServer.java:624) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.PlayerConnection.handleCommand(PlayerConnection.java:1058) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.PlayerConnection.a(PlayerConnection.java:919) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(SourceFile:37) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.PacketPlayInChat.a(SourceFile:9) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.PacketHandleTask.run(SourceFile:13) [craftbukkit.jar:git-Bukkit-f233e7d]
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_25]
    at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_25]
    at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:643) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:284) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:598) [craftbukkit.jar:git-Bukkit-f233e7d]
    at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:506) [craftbukkit.jar:git-Bukkit-f233e7d]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_25]
Caused by: java.lang.NullPointerException
    at me.porterk.mg.MortalAPI.setSpectating(MortalAPI.java:513) ~[?:?]
    at me.porterk.mg.MortalListener.onPlayerDeath(MortalListener.java:157) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_25]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_25]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:295) ~[craftbukkit.jar:git-Bukkit-f233e7d]
    ... 26 more
[18:22:23] [Server thread/INFO]: PorterK fell out of the world
[18:22:23] [Server thread/INFO]: [PorterK: Killed PorterK]

Line 513:

Code:

plugin.chat.put(p.getName(), "spectate");

Line 157:

Code:

api.setSpectating(a);

 

@ColaCraft If it's not plugin that is null, it must be plugin.chat. Do you initialize it as the plugin is enabled?

 

Did you instantiate the (incorrectly public) hashmap? With NPE's it's probably better to post full classes.

 

What is null is Player p, or whatever, even though it passes my null check. If I take out that line, I still get a NPE, just for the next time I try to do p.anything

 

@ColaCraft Even if Java magically made the mistake of letting a null object through a check, it is impossible for p to even be null in the situation it is called in, as a player from PlayerDeathEvent is never null...

Be more thorough with your debugging.

 

Sigh... if I remove the line with the plugin chat, the NPE is at p.sendMessage("");

Call it magical or impossible, but it is a reality that I am living with :/

 

@ColaCraft I'm not so sure about that. Nothing can magically pass through a null check. I'm now fairly certain that plugin is actually null because the next time you invoke a method on the player object is this line:

Code:

p.sendMessage(plugin.tag+ ChatColor.AQUA+"You are now spectating.");

You are also trying to get plugin.tag, which also might be the cause of your NPE. Add something like this and check the console :

Code:

System.out.println("Plugin equals "+plugin+", and player equals "+p); 

This will reveal which one is null.

 

o.o this is a clear sign that I have been looking at this NPE for far too long.....

@Totom3 but

Code:

Main plugin;

    public MortalAPI(Main plugin) {
        this.plugin = plugin;
    }

And I use the plugin tag at least 100 other times in that same class

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

 

@ColaCraft Nothing prevents you to pass a null argument to a constructor either. What does the console say with the debug message I posted?

 

Plugin is null -.-













...cri

 

Then don't pass a null value into the constructor...

 

Thanks for the advice...

I fixed it with this:

Code:

    public void setSpectating(Player p, Main plugin){
       
        this.plugin = plugin;

        if(p != null){
        if(spectating.size() < 10){
           
            plugin.chat.put(p.getName(), "spectate");
            p.sendMessage(plugin.tag + ChatColor.AQUA + "You are now spectating.");
            p.getInventory().clear();
           
            spectating.add(p.getName());
           
            p.setGameMode(GameMode.SPECTATOR);
        }else{
           
            for(Player s : Bukkit.getServer().getOnlinePlayers()){
                p.getInventory().clear();
                s.kickPlayer(ChatColor.DARK_RED + "Game over! " + ChatColor.GOLD + p.getName() + ChatColor.DARK_RED + " has won!");
                gameOver();
            }
        }
           
        }
       
    }

 

Yup that's what you do

 

@ColaCraft If that works then that's cool but if you later want to expand your plugin and don't fix the real issue... you'll end up passing the plugin on each method. It's not necessary, but if I was you, I'd fix this right away

 

What exactly is the real issue? I'm sure I could figure it out if I sat down and looked for long enough, but I am sitting on like 6 hours looking at plugin today, I am starting to miss things or see things that aren't there

I realize that "plugin" is null there, but I'm not sure why exactly is is null only there.

 

@ColaCraft

The issue is that you never set the member variable, or are using an instance that wasn't built with the constructor.

 

@ColaCraft We'd need the full class(es) to help you track down the issue. I guess that this can either be caused by passing a null object to the constructor, or as @mythbusterma said, using another instance.

 

@Totom3 @mythbusterma

I fixed it, thanks guys.

 

@ColaCraft And... mark as solved!