Thinking recursively :(

I need some help thinking recursively. I've never had to use this board before, but it's finals week and I'm desperate to get this project done so I can start studying. I had to modify several parts of a java heap program, but one part that's stumping me is converting one function with a while loop into a recursive function. Here's the code:

<code>
   public void trickleUp(int index)
   {
      int parent = (index-1) / 2;
      Node bottom = heapArray[index];

      while( index > 0 && heapArray[parent].getKey() > bottom.getKey() )
         {
         heapArray[index] = heapArray[parent];  // move it down
         index = parent;
         parent = (parent-1) / 2;
         }  // end while
      heapArray[index] = bottom;
   }  // end trickleUp()
</code>

How the hell do I convert this into a recursive function with a void function? My professor said the interface of the method should remain the same.

>>1
1. Learn how tail call elimination works.
2. Perform it in reverse.