CSC153, Class 39: Polymorphism

Admin:
* About my morning
* Homework 5 due
* Questions on homework 6?
* No reading this weekend
* Prospies today!  Fun

Overview:
* Inheritance, reviewed
* Polymorphism, reviewed
* A small Rational example
* Lab: O3.1, O3.2, O3.4, O3.5
* Pronounce the following words: Monticello. Nevada. Buena Vista.

Inheritance: You can build classes based on other classes and not have to type the code again.
Many benefits: Improved reliability, less code, corrections propagate ...
Another benefit: Polymorphism

Polymorphism: You can build functions/methods/procedures that act on particular kinds of things, and they'll automatically work on "related" things (members of subclasses and implementors of interfaces)
* Benefit: Easy to write functions that use a variety of objects rather than writing one kind of function for each object (code reuse, not lots of code to change when you realize you screwed up)
* Potential drawback: You have less control over what your procedure is applied to.  (Good preconditions and postconditions help.)
* Benefit: Your procedure will work on objects in classes that did not exist when you wrote your procedure.

Side note: If you make a method static, you call it with
	ClassName.methodName(...)
If you don't make a method static, you call it with
	objectName.methodName(...)

Example (see Examples directory)
Moral: Polymorphism doesn't always work the way you want it to.

* Lab: O3.1, O3.2, O3.4, O3.5