Null Pointer Exception

Hello,
I am having a NPE problem at line 58 of my arena manager code. Any help would be good!:

Code:java

package me.codenametitan.pbpt.arena;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
import me.codenametitan.pbpt.PBPTMain;
 
import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
 
public class ArenaManager{
 
    private static PBPTMain plugin;
    public ArenaManager(PBPTMain plugin) {
        ArenaManager.plugin = plugin;
    }
 
 
    public Map<String, Location> locs = new HashMap<String, Location>();
 
    public static ArenaManager a = new ArenaManager(plugin);
 
    Map<String, ItemStack[]> inv = new HashMap<String, ItemStack[]>();
    Map<String, ItemStack[]> armor = new HashMap<String, ItemStack[]>();
 
    List<Arena> arenas = new ArrayList<Arena>();
 
 
    public static ArenaManager getManager(){
      return a;
    }
 
    //get an Arena object from the list
    public Arena getArena(int i){
      for(Arena a : arenas){
          if(a.getId() == i){
              return a;
          }
      }
      return null;
    }
 
 
    public void addPlayer(Player p, int i){
      Arena a = getArena(i);
      if(a == null){
          p.sendMessage("Invalid arena!");
          return;
      }
 
      a.getPlayers().add(p.getName());
      inv.put(p.getName(), p.getInventory().getContents());
      armor.put(p.getName(), p.getInventory().getArmorContents());
      p.teleport(a.spawn);//THIS LINE IT OCCURUS
    }
 
 
    public void removePlayer(Player p){
      Arena a = null;
      for(Arena arena : arenas){
          if(arena.getPlayers().contains(p.getName())){
              a = arena;
          }
 
      }
      if(a == null || !a.getPlayers().contains(p.getName())){
          p.sendMessage("Invalid operation!");
          return;
      }
 
      a.getPlayers().remove(p.getName());
      p.getInventory().setContents(inv.get(p.getName()));
      p.getInventory().setArmorContents(armor.get(p.getName()));
 
      inv.remove(p.getName());
      armor.remove(p.getName());
      p.teleport(locs.get(p.getName()));
      locs.remove(p.getName());
    }
 
 
    public void createArena(Location l){
      int num = arenas.size() + 1;
 
      Arena a = new Arena(l, num);
      arenas.add(a);
 
      plugin.getConfig().set("Arenas" + num, serializeLoc(l));
      List<Integer> list = plugin.getConfig().getIntegerList("Arenas.Arenas");
      list.add(num);
      plugin.getConfig().set("Arenas.Arenas", list);
      plugin.saveConfig();
    }
 
    public void removeArena(int i) {
        for(String s : getArena(i).getPlayers()) {
            Player p = Bukkit.getPlayerExact(s);
            if(p != null) {
                p.teleport(locs.get(p.getName()));
                locs.remove(p.getName());
            }
        }
    }
    public boolean isInGame(Player p) {
        for(Arena a : arenas) {
            if(a.getPlayers().contains(p.getName())) {
                return true;
            }
 
        }
        return false;
    }
 
        public void loadGames() {
            if(plugin.getConfig().getIntegerList("Arenas.Arenas").isEmpty()) {
                return;
            }
 
            for(int i : plugin.getConfig().getIntegerList("Arenas.Arenas")) {
                Arena a = new Arena(deserializeLoc(plugin.getConfig().getString("Arenas" + i)), i);
                arenas.add(a);
            }
    }
 
    public String serializeLoc(Location l) {
        return l.getWorld().getName()+","+l.getBlockX()+","+l.getBlockY()+","+l.getBlockZ();
    }
 
    public Location deserializeLoc(String s) {
        String[] st = s.split(",");
        return new Location(Bukkit.getWorld(st[1]), Integer.parseInt(st[1]), Integer.parseInt(st[2]), Integer.parseInt(st[3]));
    }
 
}
 

 

You're using the name "a" for both the ArenaManager object at the top and the Arena objects farther down in the code. Could that be causing it?

Sorry if it's not the answer you need, I'm not professional enough to instantly spot any incorrect code :3

 

nuclearmissile I don't think thats the issue because the Arena object is a local variable

 

I believe it's because that code will run if the arena is null or not. It should be in an else if.
To say it another way, it will check that the arena exists. If not it will return and move on. It's moving on to the teleport code, so if the arena doesn't exist it'll still try to to them.

 

It won't move on, because it returns from the function.

My guess is a.spawn is null.

 

Last time I checked, void methods don't return...

 

Yeah, but the method isn't actually trying to return anything. Doing "return;" in a void method exits out of the method without returning anything.

 

I'm not sure you made that on your own

Otherwise, there are a few possibilities:
One, you didn't fill the list
Two, the number is not within the lsit
Three, you didn't set the spawn

 

Or 4:

Further more, if you make the method a boolean instead of void, your return should work, as long as you return a value. In your case, false.

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

 

return; escapes the method, prevents the method from executing code below it... That can't possibly cause a NPE

 

void can't return.

 

A full stack trace would help here. Looking at you code, for me the given line can't cause a NPE. Reason: a is checked for being null, so it can't be null, p is used in the lines before line 58, so it can't be null either, or the NPE is on a different line. If this line really appears in the stack trace, only a.spawn can be null as nisovin said, or there is some other circumstance not related to the parameters used in the call.

 

No, you absolutely can and are expected to use the return keyword in a void method. Void's don't return actual values, hence there being no value (such as a boolean, null or object) after the return keyword. The return keyword in java is often used in void methods as an alternative to using many nested conditional statements in a void method by exiting the block of code and not executing any code below.

 

Then why do I get an error when I return?...
Plus, it should automatically infer when you return, typically at the end of if statements, at the end of the method, and in try/catch/finally statements

 

xTrollxDudex Sorry dude. I used your code. It does the same if I use your source

 

CodenameTitan
Don't be