Generics (return type error)

Question

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

Answer 1

All two methods (Malvolio and carr_onstott) works fine, thanks a lot!
I had to modify the header of carr_onstott's method with:
public <T extends Comparable<T>> T search(T node, T root)
because it gives 2 errors, one of wich is that:
D:\UNI\Progetti\MP\1\BTNodeGen.java:191: > expected
    public <T extends Node, Comparable<T>> T search(T node, T root)
                                      ^Why it gives that error?
Thanks to Malvolio I understood what was my fault: in the sons declaration I left "<T>".
In fact with
public BTNodeGen<T> left, right;
it gives no type error and I don't need downcasts.
I always tried to pass in the key value as parameter, but without the correct son's declaration it didn't work.
When I finish to test deeply the entire structure I'll post the results and all the structure's code.
Thank you very much, I was lost without you!