The Group class is the most general-purpose of the group nodes
Has exactly one parent
Can have any number of children
You can add, insert, remove, and get children in a group
Children are implicitly numbered starting with 0
Child rendering order is up to Java 3D!
Java 3D can sort shapes for better rendering efficiency
The Group node object is a general-purpose grouping node.
Group nodes have exactly one parent and an arbitrary number of children that
are rendered in an unspecified order (or in parallel). Null children are allowed;
no operation is performed on a null child node. Operations on Group node objects
include adding, removing, and enumerating the children of the Group node. The
subclasses of Group node add additional semantics.