Programs in an Object-Oriented Language

Programs in an Object-Oriented Language
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Review

The Practice:
- We have been using an object-oriented programming language
- Our "programs" have consisted of a main class and one or more supporting classes
The Theory:
- We've used a casual definition of the term "program"
- We've avoided defining the term "object"

Moving Forward

The Theory:
- We need to define the term "object" (and the term "class")
- We need to have a more formal definition of the term "program"
The Practice:
- We need to be able to write classes (and use objects that are instances of those classes)

Programs in an Object-Oriented Language

The Structure of Object-Oriented Code:
- A group of cooperating classes with a well-defined entry point
Object-Oriented Programs When Running:
- A group of cooperating objects (some, but not all, of which are created in the entry-point)
- An optional group of utility classes that the objects use for performing calculations of various kinds
Kinds of Java Programs:
- Applications - the entry point is the main() method in the main class
- Applets - the entry point is the init() method in the Applet