Calling constructor of a generic type

Question

If I have an abstract class like this:

public abstract class Item
{
    private Integer value;
    public Item()
    {
        value=new Integer(0);
    }
           


        

Answer 1

T is an alias for the actual type your class will handle, for example if you instantiate Box then T is really just an alias for Item. As you declare T extends Item then you know that T will have at least the same interface as Item, so you can treat it like one.

I think what you really want to do is not instantiate the item field in Box, but instead implement a couple of methods to let you manipulate that field.

public class Box {
    private T item;

    public T getItem() {
        return this.item;
    }

    public void setItem(T item) {
        return this.item = item;
    }
}