Unity, that is the Ubuntu user interface, that nobody else uses.
Since it is a Ubuntu-only thing, few applications have native support for its OSX-style hipster "global" menus.
For Java, someone once wrote a hack called java-swing-ayatana, or "jayatana", that is preloaded into the JVM via the environment variable JAVA_TOOL_OPTIONS. The hacks seems to be unmaintained now.
Unfortunately, this hack seems to be broken now (Google has thousands of problem reports), and causes a NullPointerException or similar crashes in many applications; likely due to a change in OpenJDK 8.
Now all Java Swing applications appear to be broken for Ubuntu users, if they have the jayatana package installed. Congratulations!
And of couse, you see bug reports everywhere. Matlab seems to no longer work for some, NetBeans appears to have issues, and I got a number of bug reports on ELKI because of Ubuntu. Thank you, not.