Java Programming

My below code where I'm calling a stored procedure is giving a null pointer exception. On the command prompt, the same arguments work and the record is added in db but not when I call the stored procedure from inside java program

CallableStatement insertStat = db_conn.prepareCall("{call InsertCourses(?,?,?,?,?,?,?,?)}");
insertStat.setString(1, course_type.trim());
insertStat.setInt(2,Integer.valueOf(str_course_number).intValue());
insertStat.setInt(3, course_section);
insertStat.setInt(4, course_units);
insertStat.setInt(5, Integer.valueOf(course_loc.room).intValue());
insertStat.setString(6,course_loc.building);
insertStat.setString(7, course_loc.hours);
insertStat.registerOutParameter(8,checkInsert);
insertStat.execute();
checkInsert = insertStat.getInt(8);

Here is the command that works fine from inside SQL editor

call university.InsertCourses('cmpe' , 500 , 1 , 3 , 700 , 'engr' , 'MT 0400-0500' , @a);

Debugged the code to make sure that all the above variables correspond to the values above.

Any ideas what is wrong???

Thanks