Adding methods and values to existing java object

Question

I'm trying to add a function that add a unique id to an object in java. I've a function that returns me an object:
ItemStack is=ent.getKiller().getItemInHand();
I made a java class that extends ItemStack class and i tryied to cast the object to this class.

import org.bukkit.inventory.ItemStack;
import java.util.UUID;
public class UniqueItem extends ItemStack{
    private String uid="";
    public UniqueItem(){
        uid=UUID.randomUUID().toString();
    }
    public String getUniqueID(){
        return uid;
    }
}

UniqueItem is=(UniqueItem)ent.getKiller().getItemInHand();

It produce me an error and i don't undersatand why. Please help me to solve my problem or give me an alternative solution.
Thanks

ItemStack is not a UniqueItem, thus you cannot cast it that way around. But UniqueItem is a ItemStack and you can cast UniqueItem to ItemStack — TungstenX
– TungstenX, Commented Nov 15, 2015 at 12:30

Ankur Shanbhag · Accepted Answer · 2015-11-15 10:38:41Z

1

You get a ClassCastException at runtime because you are trying to cast an item which is not of type UniqueItem

Also, extending the class will not help you. Instead create a wrapper class around ItemStack object which maintains unique ID along with the object.

Try this:

// wrapper class
public class UniqueItem {
    ItemStack item;
    private String uid="";
    public UniqueItem(ItemStack item) {
        this.item = item;
        uid=UUID.randomUUID().toString();
    }

    public String getUniqueID(){
        return uid;
    }
}

answered Nov 15, 2015 at 10:38

Ankur Shanbhag

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