This is a tricky Garbage collection interview question as many programmers are not sure whether PermGen space is part of Java heap space or not and since it maintains class Meta data and String pool, whether its eligible for garbage collection or not.
By the way Garbage Collection does occur in PermGen space and if PermGen space is full or cross a threshold, it can trigger Full GC. If you look at the output of GC you will find that PermGen space is also garbage collected. This is why correct sizing of PermGen space is important to avoid frequent full GC. You can control size of PermGen space by JVM options -XX:PermGenSize and -XX:MaxPermGenSize.
