Need help with NullPointerException

I am trying to write my first mod and getting null exceptions. I am not sure where it is coming from but I guess has to do with how I am storing the data in the HashMap. Was hoping if you had a moment you could look over my code and maybe point me in the right direction.

Overview

I am trying to make a Remote Detonation Mod for TNT.
A player would equip a button in their hand and then left click the tnt to link the button to the block of tnt.
Then at a safe distance the player could left click again with the button to set off the TNT.

The enabling of the button works ok as far as I can tell but when I left click anything it gives this error in the console.

The enables seem to work ok and I get the messages fine, cant get the events to work properly. Here is the code to my two classes.

Listener

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Code:

package org.scyfi.RemoteDet;

import org.bukkit.Material;
import org.bukkit.block.Block;
import org.bukkit.entity.Player;
import org.bukkit.event.block.Action;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.event.player.PlayerListener;

public class RDListener extends PlayerListener{

    public RDListener(){
    }

    public void onPlayerInteract(PlayerInteractEvent event){

        Player player = event.getPlayer();
        Block block = event.getClickedBlock();

        if (block.getType() == Material.TNT){
            if(RemoteDet.isRemoteEnabled(player)){
                if(event.getAction() == Action.LEFT_CLICK_BLOCK && player.getItemInHand().getType() == Material.STONE_BUTTON){
                    RemoteDet.armRemote(player, block);
                    }
                else if(event.getAction() == Action.LEFT_CLICK_AIR && player.getItemInHand().getType() == Material.STONE_BUTTON && RemoteDet.isRemoteArmed(player)){
                    RemoteDet.detonateTNT(player);
                }
            }
        }
    }

}

Main class

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Code:

package org.scyfi.RemoteDet;

import java.util.HashMap;
import java.util.logging.Logger;

import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.block.Block;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.event.Event;
import org.bukkit.entity.Player;
import org.bukkit.entity.TNTPrimed;
import org.bukkit.event.Event.Priority;
import org.bukkit.plugin.PluginManager;
import org.bukkit.plugin.java.JavaPlugin;

public class RemoteDet extends JavaPlugin{

    public final Logger log = Logger.getLogger("Minecraft");
    public final String pluginName = "Remote Det";

    private RDListener blockListener;
    private static TNTPrimed tnt;

    private static HashMap<Player, Boolean> remoteEnabled = new HashMap<Player, Boolean>();
    private static HashMap<Player, Block> armedRemote = new HashMap<Player, Block>();

    public void onEnable(){
        log.info(pluginName + " - Version " + this.getDescription().getVersion() + " Enabled");
        PluginManager pm = this.getServer().getPluginManager();
        pm.registerEvent(Event.Type.PLAYER_INTERACT, blockListener, Priority.Normal, this);
        blockListener = new RDListener();

    }

    public void onDisable(){
        log.info(pluginName + " - Version " + this.getDescription().getVersion() + " has been disabled.");

    }

    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
        if (command.getName().equalsIgnoreCase("rd")) {
            if(sender instanceof Player) {
                toggleRemote((Player)sender);
            }
            return true;
        }
        return false;
    }

    public void toggleRemote(Player player){
        if(remoteEnabled.containsKey(player)){
            if(remoteEnabled.get(player)){
                remoteEnabled.put(player, true);
                player.sendMessage(ChatColor.YELLOW + "Remote Detonator enabled!");
            } else {
                remoteEnabled.put(player, true);
                player.sendMessage(ChatColor.YELLOW + "Remote Detonator disabled!");
            }
        } else {
            remoteEnabled.put(player, false);
            player.sendMessage(ChatColor.YELLOW + "Remote Detonator enabled!");
        }
    }

    public static boolean isRemoteEnabled(Player player){
        return (remoteEnabled.get(player)).booleanValue();
    }

    public static void armRemote(Player player, Block block){
            armedRemote.put(player, block);
            player.sendMessage(ChatColor.RED + "Remote is ARMED!!");
    }

    public static boolean isRemoteArmed(Player player){
        return(armedRemote.containsKey(player));
    }

    public static void detonateTNT(Player player) {
        tnt.teleport((armedRemote.get(player)).getLocation());
        (armedRemote.get(player)).setType(Material.AIR);
    }
}

I am pretty new at this so I am sure it is something stupid I am missing. Thanx for your time.

 

if the hashmap returns null (no key) you can't return a boolean value from it I believe. Also I have no idea why you are using static methods in your main plugin file when the information is required by the listener?

 

Code:

        pm.registerEvent(Event.Type.PLAYER_INTERACT, blockListener, Priority.Normal, this);
        blockListener = new RDListener();

you got those backwards.

 

I removed the static field from the methods. I also when in and added if statement for my hashmaps checks to look for presence of a key first. Still getting the same errors.

haha I hate myself....

Still getting an error but at least now it is giving me line numbers to work with. Thank you much!

Still getting NPE's from what @Kitteh was saying with my hashmap checks. Is there an easier way to do this then using Hashmap? Just use an arraylist or something?

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

 

What you're running into specifically is the fact that isRemoteEnabled is calling .booleanValue() on a pointer that may be null. You can fix it by checking for that first. Although really, instead of using a HashMap<Player,Boolean> like you are, I'd reccomend using a LinkedList<Player> and then returning remoteEnabled.contains(). Here's some code that should work:

Code:

public class RemoteDet extends JavaPlugin{

    // ...

    private static List<Player> remoteEnabled = new LinkedList<Player>();
    private static HashMap<Player, Block> armedRemote = new HashMap<Player, Block>();

    // ...

    public static void toggleRemote(Player player){
    	if(remoteEnabled.contains(player)){
            remoteEnabled.remove(player);
            player.sendMessage(ChatColor.YELLOW + "Remote Detonator disabled!");
    	} else {
    	    remoteEnabled.add(player);
            player.sendMessage(ChatColor.YELLOW + "Remote Detonator enabled!");
    	}
    }

    public static boolean isRemoteEnabled(Player player){
        return remoteEnabled.contains(player);
    }
    
    // ...
    
}

 

@Kitteh @MSC

I finally got it all working and would like to thank both of you for the help.

Source