generics (error in return type)

[silvio relli]

Hi to everyone, I'm new around there!
I have 2 questions to ask:

I tryed to implement a generic tree inside of wich I created a "search" method.
This method needs the method "compareTo" of the class "Comparable" to compare nodes, so the tree class requires a bound and the header is the following:

public class BTNodeGen <T extends Comparable>

The problem is that in this whay the search method returns a Comparable instead of a generic type. The method is the following:

public <T extends Comparable> T search(T el)
{

if (el.compareTo(key)==0)
{
return(el);
}
else if((el.compareTo(key)<0) && (left != null))
{
return ((T)left.search(el));
}
else if(right != null)
{
return ((T)right.search(el));
}
else
{
return null;
}
}

This method works and returns a T only because I added some downcast to T before the return, otherwise it gives a compile error because it is returned a Comparable where is expected a T.

How can I do to avoid downcasts (that aren't so much correct for a OO language...)?
Can you help me?


A last question: what changes between the following header of the method search:
- public <T extends Comparable> T search(T el)
- public T search(T el)

and between the following class header
- public class BTNodeGen<T extends Comparable>
- public class BTNodeGen<T extends Comparable<T>>

Thanks for all