code: Object addRightMostKey(
      Object            new1)
    {
      Object old1 = null;
  
      if (isFull())                  /* Node is currently full                */
        {                            /* We will overlay right-most key        */
          old1 = rightMostKey();
          _nodeKey[rightMostIndex()] = new1;
        }
      else
        {
          _population++;
          _nodeKey[rightMostIndex()] = new1;
          if (midPoint() > rightMostIndex())
            _nodeKey[midPoint()] = rightMostKey();
        }
  
      return old1;
    }
docs: Add the right-most key to the node.
  
  <p>Insert a new key in the right-most slot in the node.
  If this causes the right-most key to be overlayed
  it is returned to the caller.  Otherwise null is returned to the
  caller.</p>
  
  @param new1 The new key to be inserted.
  @return the key that used to be the right-most key in the node
  iff it was overlayed in the process.