FULL PRODUCT VERSION :


A DESCRIPTION OF THE PROBLEM :
The javadoc for JComponent.paintComponent specifies a contract for painting opaque components:

> if this component is opaque, you must completely fill in the background in a non-opaque color

It should read "opaque color", or "non-transparent color".

https://docs.oracle.com/javase/9/docs/api/javax/swing/JComponent.html#paintComponent-java.awt.Graphics-


REPRODUCIBILITY :
This bug can be reproduced always.