Am I able to change the code (Data class, etc) provided by Sun for the Java Developer Certification 1.2 or must I use it as it is?

Franck Rasolo

You are free to modify the provided source code as long as you document the reasons that made you do so.

Indeed, the specification for the assignment is such that people can come up with many different approaches to implementing a valid solution. For this exam (SCDJ2), more marks are awarded on making and documenting design decisions rather than on implementing production-quality software.

Tip: I suggest you join the certification study groups dedicated to this exam: