Introduction ObjectOriented Programming Reprise The Journey So Far

Introduction Object-Oriented Programming Reprise

The Journey So Far Procedural Programming using Pseudocode You are here

The Destination Procedural Programming using Pseudocode Object Oriented Programming using Java

Introduction • You have now have a taste of programming in a real language • Now we move more deeply into the Object Oriented Programming Paradigm – The Object Oriented paradigm is a significant factor in modern programming – Typical OO Languages include C++, Smalltalk and, of course, Java.

Object Oriented Programming • A different programming style • A different way of thinking • Origins – Problems with very large systems becoming unmanageable (> 100, 000 lines of code) – Graphical User Interfaces (e. g. Macintosh, Windows) required a different way of programming due to complex interactions of windows, mouse clicks, etc. – Xerox PARC: Smalltalk – C++ as an enhancement to C – Java as a Web language

To be more specific. . .

The Scenario • Recall the concept of a Queue: – – Defined by a set of behaviors Enqueue to the end Dequeue from the front First in, first out Items

Where is the Queue? • The logical idea of the queue consisted of: – Data stored in some structure (list, array, etc. ) – Modules to act on that data • But where is the queue? • We’d like some way of representing such a structure in our programs.

Why? • We would like to have reusable “drop-in” programming components we could use to solve problems. • We would like to encapsulate the data and the behaviors in order to “protect” it from misuse. • We would like clear interfaces between different parts of programs • We would like a programming system that was extensible • We would like a programming language that would be excellent for modeling real world objects

Issues • As is, there is no way to “protect” against violating the specified behaviors. Procedure Enqueue Procedure Dequeue The Queue Data Sneak into Middle

Issues • If our queue could somehow be packaged we could drop in a “queue object” whenever we needed it. Queue Acme Manufacturing

Issues • We’d like a way to put a “wrapper” around our structure to protect against intrusion. Enqueue Queue Acme Manufacturing Sneak into Middle Dequeue

Issues Contract The party of the first part hereinafter known as the queue agrees to. . . The party of the second part hereinafter known as the application agrees to. . . Clear lines of responsibility

Issues • I need a queue that can tell me how many items it contains. . . Enqueue Queue Acme Manufacturing Dequeue ic g a “M ” s s e c o Pr Enqueue Size Counting. Queue Acme Manufacturing Dequeue

Issues Elevator Signal $ Bank. Account Elevator Object Car Student Signal Object Student Object Bank. Account Object Real World Objects!

Questions • Why do we have the procedural paradigm and the object oriented paradigm? • Is procedural programming used for certain problems and object oriented programming used for others?