Summary

Node, Camera, LightBase, Shape, and Shape3D cannot be extended by user code and will be sealed.

Problem

None of these classes can be extended by user code, and any attempt to do so will fail at runtime with an exception. Since Java now supports sealed classes, we can turn a run-time error into a compile-time error.

Solution

Seal the class hierarchy and remove the run-time checks to turn this into a compile-time error instead.