When I load up a world and hover over my item, I crash with this error :

 

 

 2014-01-05 18:18:30 [iNFO] [sTDOUT] java.lang.NullPointerException
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at gmod.mods.roleplay.main.common.item.ItemLicence.addInformation(ItemLicence.java:54)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.item.ItemStack.getTooltip(ItemStack.java:663)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainer.drawItemStackTooltip(GuiContainer.java:226)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainerCreative.drawItemStackTooltip(GuiContainerCreative.java:778)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainer.drawScreen(GuiContainer.java:202)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.renderer.InventoryEffectRenderer.drawScreen(InventoryEffectRenderer.java:43)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainerCreative.drawScreen(GuiContainerCreative.java:683)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.renderer.EntityRenderer.updateCameraAndRender(EntityRenderer.java:1036)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:946)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.run(Minecraft.java:838)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.main.Main.main(Main.java:93)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at java.lang.reflect.Method.invoke(Unknown Source)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.launchwrapper.Launch.launch(Launch.java:131)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 
2014-01-05 18:18:30 [iNFO] [sTDOUT] 
2014-01-05 18:18:30 [iNFO] [sTDOUT] A detailed walkthrough of the error, its code path and all known details is as follows:
2014-01-05 18:18:30 [iNFO] [sTDOUT] ---------------------------------------------------------------------------------------
2014-01-05 18:18:30 [iNFO] [sTDOUT] 
2014-01-05 18:18:30 [iNFO] [sTDOUT] -- Head --
2014-01-05 18:18:30 [iNFO] [sTDOUT] Stacktrace:
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at gmod.mods.roleplay.main.common.item.ItemLicence.addInformation(ItemLicence.java:54)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.item.ItemStack.getTooltip(ItemStack.java:663)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainer.drawItemStackTooltip(GuiContainer.java:226)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainerCreative.drawItemStackTooltip(GuiContainerCreative.java:778)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainer.drawScreen(GuiContainer.java:202)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.renderer.InventoryEffectRenderer.drawScreen(InventoryEffectRenderer.java:43)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 	at net.minecraft.client.gui.inventory.GuiContainerCreative.drawScreen(GuiContainerCreative.java:683)
2014-01-05 18:18:30 [iNFO] [sTDOUT] 

 

 

My item code:

 

 

 package gmod.mods.roleplay.main.common.item;


import gmod.mods.roleplay.main.main_roleplay;

import java.util.List;



import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.nbt.NBTTagCompound;
import net.minecraft.tileentity.TileEntity;
import net.minecraft.world.World;

public class ItemLicence extends Item {

public ItemLicence(int par1) {
	super(par1);
	this.setCreativeTab(main_roleplay.tabRoleplay);
}

public static int theRandom;


 public ItemStack onItemRightClick(ItemStack par1ItemStack, World par2World, EntityPlayer par3EntityPlayer) {
	//here you can use the information about the itemstack nbt
	//ex:


	 if(par1ItemStack.stackTagCompound == null){
		//here we know the nbt is null
		 par1ItemStack.stackTagCompound = new NBTTagCompound();
		}else {

		 theRandom = par1ItemStack.stackTagCompound.getInteger("myRandomNumber");
			if(theRandom == 0){
				//here we DONT have anythin on the stack compound
				par1ItemStack.stackTagCompound.setInteger("myRandomNumber", (int)(Math.random()*100000));//generate a number between 0-100 and place it on the nbt
			}else{
			//	System.out.println("the number of this item is: "+theRandom);
			}
 }


			return par1ItemStack;

 }
 public void addInformation(ItemStack par1ItemStack, EntityPlayer par2EntityPlayer, List par3List, boolean par4)
 {
	        NBTTagCompound stackCompound = par1ItemStack.getTagCompound();
	        int idToDisplay = stackCompound.getInteger("myRandomNumber");
	        par3List.add("ID: " + idToDisplay);
	    }




}

 

 

 

 

Any help be appreciated

Well...if you never right-click it (which checks the nbt tag for null and if it is, sets values) what did you EXPECT to happen?

how would I stop from it becoming null, ive already tried to check if the random number is equal to 0 execute the command, and ive tried using the nbt and checking if is(not) equal to 0, then do the command give; the code is  shown here (THIS DOES NOT WORK; EXAMPLE) :

 

      
public void addInformation(ItemStack par1ItemStack, EntityPlayer par2EntityPlayer, List par3List, boolean par4) {
    
    		if(par1ItemStack.stackTagCompound.getInteger("myRandomNumber") /* != */ == 0) {
    	NBTTagCompound stackCompound = par1ItemStack.getTagCompound(); 
        int idToDisplay = par1ItemStack.stackTagCompound.getInteger("myRandomNumber");
        par3List.add("ID: " + idToDisplay);
    		}
      }

It's not BECOMING null, it hasn't ever been SET YET.  The variable DOES NOT EXIST for you to see if it is not-zero.

 

Order of operations, dude.

 

if(par1ItemStack.stackTagCompound.getInteger("myRandomNumber") /* != */ == 0) {

 

THIS WILL FAIL BECAUSE stackTagCompound IS NULL RIGHT NOW.

so what should I do from keeping it from null (NOOBIE QUESTION : )

if(par1ItemStack.stackTagCompound.getInteger("myRandomNumber") != null)

ok what then?