Is there a way to get java apps to use my gtk theme?
You can try to set Java's default look and feel to GTK:
Open a terminal ( Ctrl + Alt + T ) and paste the upper one for openjdk and the lower one for sun java .
Before and after:
If you are the developer or it's an open source, an alternative way is to change the look and feel of the application. Insert the below code in the
This may be also helpful.