At what point are you wondering if they're eligible?
They'll never be eligible for garbage collection during the main method - you have active references to them. It doesn't matter that they refer to one another - the fact that you have references to them prevents them from being garbage collected.
When the main method ends, your references go out of scope so the objects would be available for garbage collection, but, at that point, the application terminates and no garbage collection is going to happen at that point. Rather, the JVM simply exits.