Andrew Ko, whose papers I have mentioned before, observed in An exploratory study of how developers seek, relate, and collect relevant information during software maintenance tasks that
When investigating [navigations back to previously-seen code fragments], nearly all seemed to be for the purpose of juxtaposing a set of code fragments while editing many dependent fragments. … Although Eclipse supports viewing multiple files side by side, placing any more than two files side by side would have incurred the interactive overhead of horizontal scrolling within each of the views.
Meanwhile, from my user study, I believe that the Package Explorer is usually not worth its screen real estate and the Outline View is probably harmful (which I will explain below). If I close the Package Explorer and the Outline View, on my 24″ monitor, I have oodles of room for two source files side-by-side. I think that is probably the way to go.
Developers used the Package Explorer to find classes that had interesting strings in them. For example, in the Arrow task, they would do a “visual grep” to find classes that had the word “Arrow” or “Line” in them. Generally, however, they would explore the first class they found with “Arrow” or “Line” in it. While that happened to be okay in the Arrow task, it is easy to imagine situations where the first class could be uninteresting or even deceptive. I have come to the opinion that it is better in most cases to use Control-Shift-T to open the “Open Type” dialog, where you can enter in the string you are interested in. (Note that you can use wildcards, e.g. “*arrow” to find all Types that have the text “arrow” anywhere in their names.)
If you use the Open Type dialog, you will immediately (because it immediately displays matching type names as you type) have a very good idea of which / how many classes have that text in them. You are not going to miss one, and you are less likely to get distracted by the first one you see.
Now, I saw a very small number of cases where the Package Explorer was useful. For example, in the Output task, one guy looked at package names and guessed (successfully) that “proguard.io” might have something to do with IO. So I don’t think you should do away with the Package Explorer, but minimize it most of the time.
As for the Outline View, you can search for strings in the method/field names using Control-O. Just like with the Open Type dialog, you can search for strings (including wildcards). Even better, with Control-O,Control-O, you can see what methods are inherited.
I don’t think I ever saw anyone wandering aimlessly (i.e. not doing a visual grep for a specific string) around the Outline View and having any good come of it. So I don’t think the Outline View is worth the screen real estate.