On Homework 1 of CS 2011 the only allowed file extension is .java.
However, on the General Directions states that " Class names and File names should follow the following format: For homework problems, the class name should include the homework number as well as the problem number i.e. the first problem of homework 1 would have a class name of HW01P01 and file name of HW01P01.java." 
I assume that we should submit the.java file only? 

i.e HW01P01.java, HW01P02.java ... HW01P06.java