OO Slow...no!

This article talks of the experiences of converting LINPACK (FORTRAN modules to work with matrices) to Java. By taking a strictly OO approach the results were poor. However, by simply optimizing key elements and not eliminating the OO design they were able get results close to the more FORTRAN like style.

http://www.devx.com/upload/free/features/Javapro/2002/03mar02/jt0302/jt0302-1.asp