This document discusses object oriented design principles including minimizing accessibility of classes and members, favoring composition over inheritance, programming to an interface rather than an implementation, the open-closed principle of being open for extension but closed for modification, and the single responsibility and Liskov substitution principles. It also provides references and contact information for Sayed Ahmed, owner of Justetc Technologies, which provides consulting services in software development, web development, and other areas of IT and computer science.

1. OBJECT ORIENTED DESIGN PRINCIPLES
Sayed Ahmed
BSc. Engineering in Computer Science and Engineering, BUET,
Bangladesh
MSc. in Computer Science, University of Manitoba, Canada
Owner/Architect/Developer
Justetc (Just et cetera) Technologies, Canada
http://www.justetc.com
http://sayed.justetc.com

2. FREE TRAINING BY JUSTETC
 Training and Education in Bangla:
 http://Bangla.SaLearningSchool.com
 Training and Education in English:
 http://www.SaLearningSchool.com
 http://English.SaLearningSchool.com
 Ask questions and get answers
 http://Ask.JustEtc.net
 Offline IT Training:
 http://University.JustEtc.net

3. OBJECT ORIENTED DESIGN PRINCIPLES
 Minimize The Accessibility of Classes and
Members
 Favor Composition Over Inheritance
 Program To An Interface, Not An
Implementation
 The Open-Closed Principle:
 Software Entities Should Be Open For
Extension, Yet Closed For Modification

4. OBJECT ORIENTED DESIGN PRINCIPLES
 The Single Choice Principle:
 Whenever a software system must support a set
of alternatives, ideally only one class in the
system knows the entire set of Alternatives
 The Liskov Substitution Principle:
 Functions That Use References To Base (Super)
Classes Must Be Able To Use Objects Of
Derived (Sub) Classes Without Knowing It

5. REFERENCES
 I will use the following resource to
demonstrate the principles
 http://userpages.umbc.edu/~tarr/dp/lectures/
OOPrinciples.pdf

6. PROGRAM TO AN INTERFACE
 http://stackoverflow.com/questions/383947/w
hat-does-it-mean-to-program-to-an-interface
 List myList = new ArrayList(); // programming to
the List interface instead of
 ArrayList myList = new ArrayList(); // this is bad

7. OBJECT ORIENTED ANALYSIS
 Must check
 http://www.salearningschool.com/displayArticle.p
hp?table=Articles&articleID=819&title=Object%2
0Oriented%20Analysis:%20Just%20an%20Over
view

8. ADDRESSES
 Trudelle Street, Toronto, Ontario, Canada
 Shimultuly, Gazipur, Bangladesh
 Justetc Computers
 Habib Complex, 2nd Floor
 Contact us
 Sayed: sayed@justetc.net (647-624-8509)
 Rafik: rafik@justetc.com (01942747702)

9. OUR SERVICES
 I provide consulting under Justetc (Just et cetera) Technologies, Canada
 I provide consulting on
 Software Development
 Web Development
 Software Engineering
 Software and Information Architecture
 Mobile Development
 Business Analysis
 I have several years of professional experience in different areas of IT,
Computer Science, and Software & Computer Engineering
 My education and experience exposed me to many abstraction levels of
computing; from the lowest level to the highest level (electronics, digital
system design, computer networks, data communications, databases,
software engineering, software development to web development)