Welcome to the Ranch
I would suggest on Eclipse, you create a Project, then a package, then a class inside that package. You can copy and paste lots in to Eclipse; you can even copy an entire .java file into the right part of the workspace folder and Eclipse will recognise it as a class. It will show up errors like wrong package name, and allow you to correct them.
I would suggest you create a more object‑oriented version of that code, however.
Also package names should start with small letters. In which case Default will turn into a keyword, and the code won't compile. Try a different package name.