Hello forums, just a note before i start, i try to look up the answers for my questions on google before i come here to ask, and ive been trying for hours to get this to work to no avial. anyways, i have an arrayList of strings for a loot list (or atleast i think i do, every time i try to log the contents i just get a null pointer). anyways. im trying to turn the arraylist into an array so i can use it to find the closest ground item. 

here is my current function to determine if i should loot a stackable item. 

 

http://pastebin.com/rgxNpPbf

 

the arraylist is transfered from an arraylist from the gui using this.(which is called in onStart() )

 

 if(gui.UseLooting)

       {

    log("setting looting shit");

    UseLooting = true;

       

    LootListStackable = gui.StackableLootList;

       

    LootListNotStackable = gui.NonStackableLootList;

    log("DISPLAYING LISTS");

   // log(gui.StackableLootList.size());

    //log(LootListStackable.size()); commented out because they both caused null pointers

       }

 

the arraylists are declared in the gui like so

 

public ArrayList<String>  StackableLootList;

 

and contents are added to the list in the gui when a button is pushed like so

 

 StackableLootList.add(LootToAdd.getText());

 

i literally have no idea why i get a null pointer whenever i try to do anything with the array lists in my main code. please help

 

 

 

 

Edited May 21, 20169 yr by roguehippo

Post all of the relevant code so I can see your problem, and Ill answer everything in one reply.

Plz indent it properly as well, ty.

Make sure that when you declare the list you instantiate it, i.e.

public ArrayList<String> StackableLootList = new ArrayList<>();

.NET conventions in Java ..

 

Anyway, we need to see whats going on in the gui class to identify the problem

Post all of the relevant code so I can see your problem, and Ill answer everything in one reply.

Plz indent it properly as well, ty.

 

here is the code for my gui. 

 

http://pastebin.com/HUNyAuFY

 

the adding of the strings when the loot button is pressed is at line 281.

 

here is my main code. 

 

http://pastebin.com/HsuELXZi

 

the looting functions are at the bottom

 

thanks

here is the code for my gui. 

 

http://pastebin.com/HUNyAuFY

 

the adding of the strings when the loot button is pressed is at line 281.

 

here is my main code. 

 

http://pastebin.com/HsuELXZi

 

the looting functions are at the bottom

 

thanks

 

public ArrayList<String>  StackableLootList;

public ArrayList<String>  NonStackableLootList;

 

Should be

 

public ArrayList<String>  StackableLootList = new ArrayList<>();
public ArrayList<String>  NonStackableLootList = new ArrayList<>();

String[] lootArray = new String[stackableLootList.size()];

 

StackableLootList.toArray(lootArray);

 

public ArrayList<String>  StackableLootList;

public ArrayList<String>  NonStackableLootList;

 

Should be

 

public ArrayList<String>  StackableLootList = new ArrayList<>();
public ArrayList<String>  NonStackableLootList = new ArrayList<>();

 

thanks so much for getting back to me i didnt know that initializing it in this specific way was necesarry or even made a difference. is it easy to explain why this makes a difference? (i just want to make my future coding as good as possible)

thanks so much for getting back to me i didnt know that initializing it in this specific way was necesarry or even made a difference. is it easy to explain why this makes a difference? (i just want to make my future coding as good as possible)

If you don't initialize a variable before you use it, it will return as null. There are some exceptions such as int, long etc.

i guess something else is wrong because im still getting null pointers when i do anything with the grounditem

i guess something else is wrong because im still getting null pointers when i do anything with the grounditem

 

Just implement enough checks to see if the GroundItems are null? Just check out your logs there would be the exact line the program is throwing a NullPointer.

i guess something else is wrong because im still getting null pointers when i do anything with the grounditem

You have to define and do a null check before using it

Im posting here just so anyone else that has this problem can hopefully find the answer. After looking on many forums i found out the problem was actually due to an import mistake. i accidently imported like java.awt.List instead of java.util.List. -___-

Im posting here just so anyone else that has this problem can hopefully find the answer. After looking on many forums i found out the problem was actually due to an import mistake. i accidently imported like java.awt.List instead of java.util.List. -___-

classic beginner mistake