I've already replied to this, but it didn't show up on the list. So
here goes again.

You get an error  because the Double.valueOf() method returns a
Double object (note the capital letter) and you're assigning it to a
double primitive. The correct method to use would be
parseDouble which you mentioned. It should be:

dbl_hw = Double.parseDouble(hw);
dbl_rp = Double.parseDouble(rp);

If that still gives you an error, it must be something to do with J++
, which I've never used