Class 41: Polymorphism Example

Held: Monday, 14 April 2003

Summary: Today we continue our exploration of polymorphism through an extended example.

Related Pages:

• EBoard.

Notes:

• Are there questions on Exam 3? Note that I've already added a question and answer section.
• As promised, we'll spend a little more time on PrereqOr and PrereqCourse.

Overview:

• Review: What is a Prereq?
• Building the PrereqOr class.
• Building the PrereqAnd class.
• Building the PrereqCourse class.

Prerequisites

• Recall that we're looking at various aspects of a student course planner.
• We're currently focusing on ways to represent prerequisites.
• We've decided that a Prereq interface should include
  • a meets(Student terry, Semester sem)> predicate;
  • a toString() transormer; and
  • an unmet(Student terry, Semester sem) method, which returns the unmet portion of the prerequisite (or null if everything in the prerequisite is met).

The Or of Two Prerequisites

• Our first implementation involves or'ing two prerequisites.
• The prerequisite holds if either prerequisite holds.

The And of Two Prerequisites

• Very similar to the previous one.

Base Prerequiste: A Course

• Depends very much on our implementation of Student.