If class A extends B then A automatically gets all methods & instance variables from B.
A can also add new methods or redefine the "inherited" methods.
When redefine methods, can call original version from superclass:
super.meth(a,b)With constructors, simply write
super(...)to first execute the constructor of the superclass.
See examples with Position and RowOrderPosn as well as CurDoublyLinkedList as extension of DoublyLinkedList.