NullPointerException Error

I'm trying to write a plugin that whenever someone crafts a certain type of item, such as pickaxes, swords, chestplates etc.. that it adds 'Crafted by <player-name>', but I keep getting an NullPointerException error. Someone explained that I have to find the ItemMeta before I can say that it is equal to Null, which I thought would be easy at first, but I can't figure it out for the life of me. If someone could show me how it's done, that would be greatly appreciated!

Code:

@EventHandler
public void onCraftingItem(PrepareItemCraftEvent e) {
ItemStack result = e.getInventory().getResult();
ItemMeta itemMeta = result.getItemMeta();
List<String> lore = itemMeta.getLore();
if (result.getType().name().contains("SWORD") && lore == null) {
lore = new ArrayList<String>();
}
Player p = (Player)e.getInventory().getHolder();
lore.add("crafted by " + p.getName());
itemMeta.setLore(lore);
result.setItemMeta(itemMeta);
e.getInventory().setResult(result);

}

 

@Rident
What line exactly is throwing the NPE?

 

@Zombie_Striker
I believe it's line 24? but I'm not entirely sure. I posted the error I get below, thanks for helping by the way!

Edit: Line 24 is: lore.add("crafted by " + p.getName());

Code:

[23:50:56 ERROR]: Could not pass event PrepareItemCraftEvent to CraftedBy v0.42
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at org.bukkit.craftbukkit.v1_10_R1.event.CraftEventFactory.callPreCraftEvent(CraftEventFactory.java:765) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.CraftingManager.craft(CraftingManager.java:314) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.ContainerWorkbench.a(ContainerWorkbench.java:57) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.InventoryCrafting.setItem(InventoryCrafting.java:120) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.Slot.set(Slot.java:58) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at org.bukkit.craftbukkit.v1_10_R1.inventory.CraftInventoryView.setItem(CraftInventoryView.java:54) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.Container.a(Container.java:200) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.PlayerConnection.a(PlayerConnection.java:1822) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.PacketPlayInWindowClick.a(SourceFile:33) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.PacketPlayInWindowClick.a(SourceFile:10) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_121]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_121]
        at net.minecraft.server.v1_10_R1.SystemUtils.a(SourceFile:45) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:732) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:400) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:668) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:567) [spigot-1.10.jar:git-Spigot-de459a2-51263e9]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_121]
Caused by: java.lang.NullPointerException
        at rident.github.io.CraftedBy.CraftingItemListener.onCraftingItem(CraftingItemListener.java:24) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_121]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_121]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_121]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[spigot-1.10.jar:git-Spigot-de459a2-51263e9]

 

@Rident Try null-checking before you do result.getType(), because what if there is no result? I doubt it's the p.getName().

 

@Drkmaster83 If I add the 'if' statement below to before the 'result.getType', I still get a NullPointerException error for the same line.

Code:

ItemStack result = e.getInventory().getResult();
ItemMeta itemMeta = result.getItemMeta();

if (itemMeta.equals(null)) {
        if (result.getType().name().contains("SWORD") && lore == null) {
        lore = new ArrayList<String>();
        }
}

 

@Rident You should null check anything that may return null in a certain scenario, especially with event listeners and command arguments .

 

@timtower so I should check if both itemMeta and result are null then? If I do the 'if' statement below, I no longer get errors, but it doesn't add 'Crafted by <player-name>' anymore.

Edit: I guess since I'm checking if result is null, it doesn't give me anything? perhaps.
Edit 2: Also, if I do 'result == null' instead of 'result.equals(null)' I get a dead code error.

Code:

    if (result.equals(null) && itemMeta.equals(null)) {
        if (result.getType().name().contains("SWORD") && lore == null) {
            lore = new ArrayList<String>();
        }
    }

 

I just edited my last post, but whenever I do 'result == null' instead of 'result.equals(null)' I get a dead code error.

 

@timtower

Here's everything I've got thus far.

Show Spoiler Hide Spoiler

Code:

package rident.github.io.CraftedBy;

import java.util.ArrayList;
import java.util.List;

import org.bukkit.ChatColor;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.inventory.PrepareItemCraftEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;
import org.bukkit.plugin.java.JavaPlugin;

public class CraftedBy extends JavaPlugin {
  
    @EventHandler
    public void onCraftingItem(PrepareItemCraftEvent e) {
    ItemStack result = e.getInventory().getResult();
    ItemMeta itemMeta = result.getItemMeta();
    List<String> lore = itemMeta.getLore();
  
    if (result.equals(null) && itemMeta.equals(null)) {
        if (result.getType().name().contains("SWORD") && lore == null) {
            lore = new ArrayList<String>();
        }
    }
  
    Player player = (Player)e.getInventory().getHolder();
    lore.add(ChatColor.WHITE + "Crafted by " + player.getName());
    itemMeta.setLore(lore);
    result.setItemMeta(itemMeta);
    e.getInventory().setResult(result);

    }
}

 

So something like this then?

Edit: That code solved my NPE error, but now nothing has 'Crafted by <player-name>' on it. I'm going to try changing the '.name.contains("SWORD")' to an actual material, to see if that works.

Code:

    if (result.hasItemMeta() && result.getItemMeta() == null && result.getType().name().contains("SWORD")); {
        if (itemMeta.hasLore() && lore == null) {
            lore = new ArrayList<String>();
        }
    }

Edit 2: I was able to figure it out. I didn't end up having to check if anything was null. Supposedly because I had written 'List<String> lore = itemMeta.getLore();' and had 'lore = new ArrayList<String>();' whenever the result had the word "SWORD" in it, it would cause 'lore.add(ChatColor.WHITE + "Crafted by " + player.getName());' to spew out the NPE error. I changed 'List<String> lore = itemMeta.getLore();' to 'List<String> lore = new ArrayList<>();' and added 'lore.add(ChatColor.WHITE + "Crafted by " + player.getName());' to my 'if' statement, which solved everything!