C SC 205 Lecture 2: More OO Concepts
major resources: Data Structures and the Java Collections Framework Second Edition, William Collins, McGraw-Hill, 2005
Introduction to Programming and OO Design using Java, Niño and Hosch, Wiley & Sons, 2002

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Wednesday September 12 (week 1)

More OO Concepts

• inheritance
• single and multiple inheritance, and the problem with multiple
• polymorphism and dynamic binding
• subclass substitution
• Where an object of a given type is called for, an object of any of its subtypes can be substituted
• example: argument type is subclass of parameter type
• example: assignment sender (right hand side) is subclass of receiver (left hand side)
• goes hand in hand with polymorphism

Unified Modeling Language (review)

OO concepts specific (but not exclusive) to Java

• interface -- a pure specification
• classes that implement an interface
• Note: a Java class can implement more than one interface but can extend only one class
• abstract classes versus interfaces
• Object versus reference equality for objects (equals versus ==, and the default)
• method overloading versus overriding

Javadoc

• basic tags
• invoking Javadoc from command line or jGRASP
• examples

The Employer and Company class hierarchies (case study handout from Collins chap 1)

• interface Employee
• class FullTimeEmployee implements Employee
• class HourlyEmployee extends FullTimeEmployee
• class Company
• class HourlyCompany extends Company
• this case study illustrates all the general and Java OO concepts covered so far

Exceptions -- Review, but here are extensive notes