Solved Check if user is Null - NPE Error

Hi everyone, I am getting a strange NPE error, I've tried so many things, and still I am getting no where. I am typing "/coin bal <a null username>" Im doing that on purpose to check to see if it will catch it, while it does, it won't print the "Could not find player", rather it will give me an NPE.

The snippet of code that is troubling me is as follows:

Code:

 if (args.length == 2) {
            Player target = Bukkit.getServer().getPlayer(args[1]);
            String stringTarget = target.getName();
            if (stringTarget != null) {
            sender.sendMessage(ChatColor.GREEN + "Player " + stringTarget + " has a current token balance of: " + ChatColor.RED + Main.econ.getBalance(target.getName()) + " Token(s)");
            }
        } else {
            sender.sendMessage(ChatColor.RED + "Could not find player");
        }

The error is as follows:

Code:

[19:19:46 INFO]: ReeseNator issued server command: /token bal s
[19:19:46 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'token' in plugin Bytetoken v0.1
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:641) ~[spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(PlayerConnection.java:1162) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:997) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_66]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_66]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:715) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_66]
Caused by: java.lang.NullPointerException
        at net.reesenator.Bytetoken.commands.Bytetoken.onCommand(Bytetoken.java:3) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot-1.8.8.jar:git-Spigot-db6de12-18fbb24]
        ... 15 more

Please help me fix this!

~ Reese

 

What is on line 3?

 

The problem is that if that player doesn't exist, target will be null and you're trying to use the getName method on a null object. You need to check if the target is null or surround that part (line 3) with a try catch for a NullPointerException.

 

I just made it easier to reference, it's line 3 on the snippet.

Could you provide me with an example so I have some reference?

~ Reese

 

@xMakerx

Why in the world would you catch a NullPointerException? Just why? Are you really that lazy that you can't be bothered to write code correctly?

@ReeseNator

Don't listen to him, that's some really awful advice.

Instead, check to see if something is null. Read this thread: https://bukkit.org/threads/how-to-r...ubleshoot-your-own-plugins-by-yourself.32457/

 

Or you can do

Code:

if (args.lenght == 2) {
  Player target = Bukkit.getServer().getPlayer(args[1]);
  if (target != null) {
    //doStuff
    return true;
  }
sender.sendMessage("FAILURE!");

This will check if the args lenth is 2 and the player is availible if not send a message to sender.
I know spoonfeeding is bad but, if you gotta see or learn the code sometime I also did a small explanation.

 

"Hey, you need to learn how to write your own code, so I'll make sure you don't have to!". You should never have to have the code in order to know how to make it.

BTW, If you cant explain what to do without showing code, either you don't know what you're doing or are too lazy to make sure the other person knows what he's doing.

 

Guys, I fixed it!

For anyone else who was in my situation, here is how to do it:

Code:

if (args.length == 2) {
            Player target = Bukkit.getServer().getPlayer(args[1]);
            if (target != null) {
                String stringTarget = target.getName(); //Get the name AFTER you confirm the player isnt null
                sender.sendMessage(plugin.getFormat() + ChatColor.GREEN + "Player " + stringTarget + " has a current token balance of: " + ChatColor.RED + Main.econ.getBalance(target.getName()) + " Token(s)");
            } else {
                sender.sendMessage(plugin.getFormat() + ChatColor.RED + "Could not find player: " + args[1]);
            }
        }

Also, if you guys don't mind, I have one last question in regards to vault. Is there a way to save a deposited amount to a config file? Here is where I am stuck:

Code:

@SuppressWarnings("deprecation")
    @EventHandler
    public void onPlayerJoin(PlayerJoinEvent event) {
        if (Bukkit.getServer().getOnlinePlayers().size() == 1) {
            Player target = event.getPlayer();
            String targetName = target.getName();
            econ.depositPlayer(target.getName(), 100); //<-- How do I save that in my config?
            target.sendMessage("You have 100 tokens");
        }
    }

Hope you all can help me some more! I'd also like to thank you all who have already helped!

~ Reese

 

@ReeseNator
Mark thread as solved if your problem has been solved.

 

Alright

 

It's an option and that isn't incorrect code. There's multiple ways to do things in programming and you should know that, @mythbusterma.

 

@xMakerx

And some of them are wrong. For example, catching RuntimeExceptions. There is never a reason to do it.

 

And using statics to share changing/temporary variables!

 

Doesn't make them wrong. Yes, it is bad practice, I just said you could do either one. There's a difference between being wrong and having bad practice. Bad practice is when something isn't recommended and wrong is when something won't work, at least to my understanding.