If class Foo provides a main method, and class Bar extends Foo but does
not provide a main method, Bar inherits Foo's main.

This is not recognized by the java command. If one invokes "java Bar"
it will complain that it cannot find a main method. It should just
invoke Foo.main.

This allows people to write a general class that drives subclasses and
then let the subclass override certain methods. A very nice capability