The menu bar appears to be broken on Ubuntu 16.04. In addition, most buttons have no padding and are very hard to read. Please see the images in the imgur album below. I also saw these messages while installing eclipse so maybe they have something to do with this:
Sorry that you are seeing this problem. Thank you for the screenshot.
We could not replicate the problem on Ubuntu 16.04 at our end.
Can you please share with us the Eclipse version details from Help > About Eclipse section?
Also let us know which desktop environment you are working with and the Java version which is used to run Eclipse.