commit eclipse project
Commit first design of cp1.
Add a fly method to supper class to add fly functionality to duck.It
make all duck can fly, but some ducks can not fly actually, it is a
wrong design.
Second design, now we separate fly and quack with interface. Only the
ducks need fly or quack to implement the interface. But another new bug
rises, if we change the fly to another behavior, all the subclass have
to change! It is not flexible.