Phenomenon and Concept

A phenomenon is a thing in the “real” world that has individual existence.

an object

A concept is a generalization, derived from a set of phenomena and based on the common properties of these phenomena.

a class

Characteristics of a concept

A name
Intension, the set of properties of the phenomenon
Extension, the set of phenomena covered by the concept

Classification and Exemplification, Examples

• hat, 23, 34, mouse, telephone, book, 98, 45.34, hello

numbers: 23, 34, 98, 45.34
words: hat, mouse, telephone, book, hello

mouse, tyrannosaurus rex, allosaurus, elephant, velociraptor

dinosaur: tyrannosaurus rex, allosaurus, velociraptor
mammal: mouse, elephant

A classification is a description of which phenomena that belongs to a concept.
An exemplification is a phenomenon that covers the concept

Comments

Generalization and Specialization

Generalization creates a concept with a broader scope. Specialization creates a concept with a narrower scope. Reusing the interface! Inheritance: get the interface from the general class. Objects related by inheritance are all of the same type.

Polymorphism and Dynamic Binding

Polymorphism: One piece of code works with all shape objects. Dynamic binding: How polymorphism is implemented Take previous Shape class hierarchy remove inheritance remove general and abstract class Shape

History of Java

1990 Oak (interactive television, big failure) 1994 Java (for the Internet) Main feature: "Write Once, Run Any Where" => wrap the operating system so they all look the same Designed for A fresh start (no backward compatibility) “Pure” OOP: C++ Syntax, Smalltalk style Improvements over C++ much harder to write a bad program Internet programming Very hard to create a virus Run in a web browser (and at the server) There is a speed issue (from Java 1.3 and up much better) C# Microsoft's “Java-Killer” project release 2001 Language very similar to Java  Commen-Language Runtime (CLR) supports 30+ languages

JAVA

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