Question

I tried printStackTrace and I have coverted everything to static (I think)… however, lines 17 and line 38 are the problem… because of this error:

You picked up: Pickaxe
java.lang.NullPointerException
        at item.addInv(item.java:38)
        at item.main(item.java:17)
Description: Can be used to mine with.
Press any key to continue . . .

Line 17: anItem.addInv(1);

Line 38: arr.add("Dan");

And here is my code:

import java.io.*;
import java.util.*;
import javax.swing.*;

public class item
{
    public static int attack, defense;
    public static ArrayList<String> arr;
    public static String name, desc, typeOf, attackAdd, defenseAdd, canSell, canEat,earnedCoins,canEquip;

    String stats[];

    public static void main(String args[])
    {
        item anItem = new item();
        ArrayList<String> arr = new ArrayList<String>();
        anItem.addInv(1);
    }

    public static void addInv(int e) {
        String iname = getItem(1)[0];
        String idesc = getItem(1)[1];
        int itypeOf = Integer.parseInt(getItem(1)[2]);
        int iattackAdd = Integer.parseInt(getItem(1)[3]);
        int idefenseAdd = Integer.parseInt(getItem(1)[4]);
        boolean icanSell = Boolean.parseBoolean(getItem(1)[5]);
        boolean icanEat = Boolean.parseBoolean(getItem(1)[6]);
        int iearnedCoins = Integer.parseInt(getItem(1)[7]);

        attack = attack + iattackAdd;
        defense = defense + idefenseAdd;
        System.out.println("You picked up: " + iname);
        try {
            arr.add("Dan");
        } catch(NullPointerException ex) {
            ex.printStackTrace();
        }

        System.out.println("Description: " + idesc);
    }

    public static String[] getItem(int e) {

        String[] stats = new String[7];

        String name = "Null";
        String desc = "None";
        String typeOf = "0";
        String attackAdd = "0";
        String defenseAdd = "0";
        String canSell = "true";
        String canEat = "false";
        String earnedCoins = "0";

        if (e == 1) {
            name = "Pickaxe";
            desc = "Can be used to mine with.";
            typeOf = "2";
            attackAdd = "2";
            earnedCoins = "5";
        }

        return new String[] { name, desc, typeOf, attackAdd, defenseAdd, canSell, canEat, earnedCoins};
    }
}

As you can see, it’s those lines and I don’t know what to do… :\

Answer 1

String canEat = "false"; Why are you converting to and from strings?

You seem to have muddled an item class an inventory class.

Perhaps an Enum would be better:

public enum InventoryItem
{
    PICKAXE("Pickaxe", "Can be used to mine with", ItemType.Tool,
            5, 2, 0)

    EPIC_PICKAXE("Super mega awesome Pickaxe", "Can be used to mine with, but epically", ItemType.Tool,
            1000000, 100, 0)


    public static enum ItemType {
        TOOL,
        WEAPON
    }

    public final String name, description;
    public final ItemType type;
    public final boolean canSell, canEat, canEquip;
    public final int earnedCoins, attackAdd, defenseAdd;

    private InventoryItem(String name, String description, ItemType type
                          int earnedCoins, int attackAdd, int defenseAdd,
                          boolean canSell, boolean canEat, boolean canEquip)
    {
        this.name        = name;
        this.description = description;
        this.type        = type
        this.canSell     = canSell;
        this.canEat      = canEat;
        this.canEquip    = canEquip;
        this.earnedCoins = earnedCoins;
    }

    private InventoryItem(String name, String description, ItemType type
                          int earnedCoins, int attackAdd, int defenseAdd)
    {
        this(name, description, type,
             earnedCoins, attackAdd, defenseAdd,
             true, false, true);
    }
}

Then you can just have List<InventoryItem> inventory = new ArrayList<InventoryItem>() within your player’s class, and directly interface with that.