It is often convenient to write the operations on trees as recursive methods. This is because the tree is itself defined recursively.

These recursive methods generaly need to have a Node as a parameter!

Consequently, these methods can't be public.

So the pattern that arises is to have one public method that doesn't require a Node parameter and to have a private recursive method that is called to do all the work.

For example, here is a pair of get methods, one public and one private:

public Value get(Key k)
{
  // Call the private recursive find 
  // starting at the root of the tree.
  return get( k, root);
}

private Value get(Key k, Node t)
{
  if ( t == null ) {
      return null;
  }
  if ( k.compareTo(t.key) < 0 ) {
      return find(x, t.left);
  }
  else if ( k.compareTo(t.key) > 0 ) {
      return find(x, t.right);
  }
  else  {
      return t.key;
  }
}