Create A Dictionary In Java Using Search Trees

I have to create a dictionary in java using search trees. I have problems with the methods put() and remove(). Working properly, ie correctly adds a new element and eliminates correctly. But I should improve a few things.

As you can see from the interface, both methods must return an element of type V, that is:

- case put(): returns the previous value associated with key (or null if the key was not associated with any value)
- case remove(): returns the value associated with the key (or null if the key was not present in the dictionary)

I do not understand how come my put method always returns null even though in reality I make him return node.getElement().

Instead, the remove() method does not know how to modify it to make sure it returns the value associated with the key. If I change the helper method return value in V (instead of Node<K, V>) method does not work anymore...

How can I then edit these two methods?

Class SearchTree:
public class SearchTree<K extends Comparable, V> implements Dictionary<K, V> {
public int size;
public Node<K, V> root;
public SearchTree() {
root = null;
size = 0;

[Code] ....