Nsryjdtyk

I have an Item class. Each Item object is held in an instance of the ItemNode class. ItemNode is an inner class in my CustomList class.

My Item class has an attribute named amount. This refers to how many of that type of Item are owned by the user

My ItemNode class also has an attribute named amount. I want the ItemNode's amount attribute to always equal the amount attribute of the Item object it holds.

In other words, (ItemNode.amount == ItemNode.item.amount), should always be true, even if I change the value of itemNode.amount later on.

How can I make Java have the same identity for both ItemNode.amount and Item.amount?

My ItemNode Class:

/**

 * Creates nodes to hold Item objects.

 */

private class ItemNode {

   // the object being held by the node

   private Item item;

   // The type of the object

   private String typeName;

   // How many are owned by the player

   private int amount;

   // What the item-subclass's name is

   private String itemName;

   // the node after this

   private ItemNode next;



   ItemNode(Item item) {



      this.data = item;

      this.typeName = typeName;

      this.itemName = item.getItemName();

      this.amount = item.getAmount();

      this.next = null;

   }

}

Don't give your ItemNode class an amount field as by doing this you're creating "parallel fields" and must take pains to make sure that they stay in sync, when in fact they can fall out of sync easily. Instead and much more simply give your ItemNode class a public getAmount() method that simply calls and returns its item's getAmount() method. Same if you need setter methods. Remember to make your code as idiot-proof as possible. Also look into the Decorator design pattern as this problem seems to be partially solved by this.

public interface Amountable {



    int getAmount();



    void setAmount(int amount);



}

public class Item implements Amountable {

    private int amount;



    public Item(int amount) {

        this.amount = amount;

    }



    @Override

    public int getAmount() {

        return amount;

    }



    @Override

    public void setAmount(int amount) {

        this.amount = amount;

    }



}

public class ItemNode<T extends Amountable> implements Amountable {

    private T item;



    public ItemNode(T item) {

        this.item = item;

    }



    @Override

    public int getAmount() {

        return item.getAmount();

    }



    @Override

    public void setAmount(int amount) {

        item.setAmount(amount);

    }    



    public T getItem() {

        return item;

    }

}