Glad you liked the article - hopefully we can sort out what's going on...
If you follow the link from the first part of the article you will find the TextEdit sample project. Controller.java is simply one of the files used in that project. (
When you follow the steps outlined in the "Getting Started with Eclipse" section, you should see all of the java files in the eclipse Navigator panel ( or the Package Explorer if you prefer it :-) So you should be able to see Controller.java there.
If it's not showing up, make sure it's actually there on disk in the first place and hasn't been accidentally deleted at some point!
Let me know how it goes for you,