How often do you find yourself cruising to code that is not properly formatted? Or that imports unnecessary packages?
I must say that I find it quite often and, as annoying as it can be it is also quite easy to enforce under Eclipse.
To have Eclipse automatically clean your source code after every save, simple enable it in:
Windows and Linux: Window -> Preferences -> Java -> Editor -> Save Actions
OS X: Eclipse (or app name if using STS, JBoss Dev Studio, etc) -> Preferences -> Java -> Editor -> Save Actions