In Notepad++ if you double click a word to highlight it, all the occurrences of the word in the file are also highlighted, a feature that is quite handy for finding where variables are declared/used.
Does the eclipse editor have this functionality? :) If so, how can I turn it on?
For the Eclipse Java editor, you can go to Window->Preferences in the menu, then Java->Editor->Mark Occurrences in the options tree and check off anything you want highlighted in this way.
Note that the editor understands Java scoping rules, so if you have 2 local variables with the same name in two different functions, it will only highlight within the current function.