Java Swing is very import when you develop Desktop Applications using Java language for making Graphical User Interfaces. Probably developers use Eclipse for developing Java Applications. However, by default Eclipse doesn't contains Graphical User Interface design tool on it. As a result of that we need to manually add Window Builder to Eclipse.
Most of programmers had encountered not responding problems in eclipse while developing mostly Java Swing Applications. Most probably these kind of errors occurs due to less java heap size.
So, If you can change this java heap size, then you will be able to improve the performance.