Eclipse, Luna, adding files

[MadDogOkie]

I have two source files (*.java) in the same directory. The first source file (checkin) is a java project, the second one
(groupUtil) is just a java file. How do I add the groupUtil java file to the check_in project. Right now I have the compile error "the selected method "getSelectedButtontext( ButtonGroup) is undefined for the type checkin". The method getSelectedButtonGroup is in the src file for groupUtil. Both java files have the same package name.