I was doing exercise 3_02 and I noticed that in the section "Handle the event object in the main application" I had to first write the properties of the ShowPreview class and then import the class. In this way I could NOT use auto-completion for the properties! I see importing first the class as a good programming style, if the IDE does not do it automatically. Sometimes it takes long to write by myself the properties and I am already acquainted with autocompletion with Java in Eclipse.
So one suggestion for improving the turorial would be to import the classes first (maybe after their declaration) and then use them.