Why can't I pass an object of type T to a method on an object of type <? extends T>?
- by Matt
In Java, assume I have the following class Container that contains a list of class Items:
public class Container<T>
{
private List<Item<? extends T>> items;
private T value;
public Container(T value)
{
this.value = value;
}
public void addItem(Item item)
{
items.add(item);
}
public void doActions()
{
for (Item item : items)
{
item.doAction(value);
}
}
}
public abstract class Item<T>
{
public abstract void doAction(T item);
}
Eclipse gives the error:
The method doAction(capture#1-of ? extends T) in the type Item is not applicable for the arguments (T)
I've been reading generics examples and various postings around, but I still can't figure out why this isn't allowed. Eclipse also doesn't give any helpful tips in its proposed fix, either. The variable value is of type T, why wouldn't it be applicable for ? extends T?.
