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Introduction to Object-Oriented Programming & Design Principles (TCF 2014)

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An introduction to Object-Oriented Programming and Design Principles that form the basis for Design Patterns.

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Introduction to Object-Oriented Programming & Design Principles (TCF 2014)

  1. 1. 1 Introduction to OOP & Design Principles Trenton Computer Festival March 15, 2014 Michael P. Redlich @mpredli about.me/mpredli/ Sunday, March 16, 14
  2. 2. Who’s Mike? • BS in CS from • “Petrochemical Research Organization” • Ai-Logix, Inc. (now AudioCodes) • Amateur Computer Group of New Jersey • Publications • Presentations 2 Sunday, March 16, 14
  3. 3. Objectives (2) • Object-Oriented Programming • Object-Oriented Design Principles • Live Demos (yea!) 3 Sunday, March 16, 14
  4. 4. Object-Oriented Programming (OOP) 4 Sunday, March 16, 14
  5. 5. Some OOP Languages • Ada • C++ • Eiffel • Java • Modula-3 • Objective C • OO-Cobol • Python • Simula • Smalltalk • Theta 5 Sunday, March 16, 14
  6. 6. What is OOP? • A programming paradigm that is focused on objects and data • as opposed to actions and logic • Objects are identified to model a system • Objects are designed to interact with each other 6 Sunday, March 16, 14
  7. 7. OOP Basics (1) • Procedure-Oriented • Top Down/Bottom Up • Structured programming • Centered around an algorithm • Identify tasks; how something is done • Object-Oriented • Identify objects to be modeled • Concentrate on what an object does • Hide how an object performs its task • Identify behavior 7 Sunday, March 16, 14
  8. 8. OOP Basics (2) • Abstract Data Type (ADT) • user-defined data type • use of objects through functions (methods) without knowing the internal representation 8 Sunday, March 16, 14
  9. 9. OOP Basics (3) • Interface • functions (methods) provided in the ADT that allow access to data • Implementation • underlying data structure(s) and business logic within the ADT 9 Sunday, March 16, 14
  10. 10. OOP Basics (4) • Class • Defines a model • Declares attributes • Declares behavior • Is an ADT • Object • Is an instance of a class • Has state • Has behavior • May have many unique objects of the same class 10 Sunday, March 16, 14
  11. 11. OOP Attributes • Four (4) Main Attributes: • data encapsulation • data abstraction • inheritance • polymorphism 11 Sunday, March 16, 14
  12. 12. Data Encapsulation • Separates the implementation from the interface • A public view of an object, but implementation is private • access to data is only allowed through a defined interface 12 Sunday, March 16, 14
  13. 13. Data Abstraction • A model of an entity • Defines a data type by its functionality as opposed to its implementation 13 Sunday, March 16, 14
  14. 14. Inheritance • A means for defining a new class as an extension of a previously defined class • The derived class inherits all attributes and behavior of the base class • “IS-A” relationship • Baseball is a Sport 14 Sunday, March 16, 14
  15. 15. Polymorphism • The ability of different objects to respond differently to the same function • From the Greek meaning “many forms” • A mechanism provided by an OOP language as opposed to a programmer- provided workaround 15 Sunday, March 16, 14
  16. 16. Advantages of OOP • Interface can (and should) remain unchanged when improving implementation • Encourages modularity in application development • Better maintainability of code • Code reuse • Emphasis on what, not how 16 Sunday, March 16, 14
  17. 17. Classes (1) • A user-defined abstract data type • Extension of C structs • Contain: • constructor • destructor • data members and member functions (methods) 17 Sunday, March 16, 14
  18. 18. Classes (2) • Static/Dynamic object instantiation • Multiple Constructors: • Sports(void); • Sports(char *,int,int); • Sports(float,char *,int); 18 Sunday, March 16, 14
  19. 19. Classes (3) • Class scope (C++) • scope resolution operator (::) • Abstract Classes • contain at least one pure virtual member function (C++) • contain at least one abstract method (Java) 19 Sunday, March 16, 14
  20. 20. Classes (3) • Abstract Classes • contain at least one pure virtual member function (C++) • contain at least one abstract method (Java) 20 Sunday, March 16, 14
  21. 21. Abstract Classes • Pure virtual member function (C++) • virtual void draw() = 0; • Abstract method (Java) • public abstract void draw(); 21 Sunday, March 16, 14
  22. 22. Class Inheritance 22 Sunday, March 16, 14
  23. 23. Static Instantiation (C++) • Object creation: • Baseball mets(“Mets”,97,65); • Access to public member functions: • mets.getWin(); // returns 97 23 Sunday, March 16, 14
  24. 24. Dynamic Instantiation (C++) • Object creation: • Baseball *mets = new Baseball(“Mets”,97,65); • Access to public member functions: • mets->getWin(); // returns 97 24 Sunday, March 16, 14
  25. 25. Dynamic Instantiation (Java) • Object creation: • Baseball mets = new Baseball(“Mets”,97,65); • Access to public member functions: • mets.getWin(); // returns 97 25 Sunday, March 16, 14
  26. 26. Deleting Objects (C++) Baseball mets(“Mets”,97,65); // object deleted when out of scope Baseball *mets = new Baseball(“Mets”,97,65); delete mets; // required call 26 Sunday, March 16, 14
  27. 27. Deleting Objects (Java) Baseball mets = new Baseball(“Mets”,97,65); // automatic garbage collection or: System.gc(); // explicit call 27 Sunday, March 16, 14
  28. 28. Object-Oriented Design Principles 28 Sunday, March 16, 14
  29. 29. What are OO Design Principles? • A set of underlying principles for creating flexible designs that are easy to maintain and adaptable to change • Understanding the basics of OOP isn’t enough 29 Sunday, March 16, 14
  30. 30. Some OO Design Principles (1) • Encapsulate WhatVaries • Program to Interfaces, Not Implementations • Favor Composition Over Inheritance • Classes Should Be Open for Extension, But Closed for Modification 30 Sunday, March 16, 14
  31. 31. Some OO Design Principles (2) • Strive for Loosely Coupled Designs Between Objects That Interact • A Class Should Have Only One Reason to Change 31 Sunday, March 16, 14
  32. 32. Encapsulate What Varies • Identify and encapsulate areas of code that vary • Encapsulated code can be altered without affecting code that doesn’t vary • Forms the basis for almost all of the original Design Patterns 32 Sunday, March 16, 14
  33. 33. 33 // OrderCars class public class OrderCars { public Car orderCar(String model) { Car car; if(model.equals(“Charger”)) car = new Dodge(model); else if(model.equals(“Corvette”)) car = new Chevrolet(model); else if(model.equals(“Mustang”)) car = new Ford(model); car.buildCar(); car.testCar(); car.shipCar(); } } Sunday, March 16, 14
  34. 34. Program to Interfaces, Not Implementations • Eliminates being locked-in to a specific implementation • An interface declares generic behavior • Concrete class(es) implement methods defined in an interface 34 Sunday, March 16, 14
  35. 35. 35 // Dog class public class Dog { public void bark() { System.out.println(“woof”); } // Cat class public class Cat { public void meow() { System.out.println(“meow”); } } Sunday, March 16, 14
  36. 36. 36 // Animals class - main application public class Animals { public static void main(String[] args) { Dog dog = new Dog(); dog.bark(); Cat cat = new Cat(); cat.meow(); } } // output woof meow Sunday, March 16, 14
  37. 37. 37 // Animal interface public interface Animal { public void makeNoise(); } Sunday, March 16, 14
  38. 38. 38 // Dog class (revised) public class Dog implements Animal { public void makeNoise() { bark(); } public void bark() { System.out.println(“woof”); } // Cat class (revised) public class Cat implements Animal { public void makeNoise() { meow(); } public void meow() { System.out.println(“meow”); } } Sunday, March 16, 14
  39. 39. 39 // Animals class - main application (revised) public class Animals { public static void main(String[] args) { Animal dog = new Dog(); dog.makeNoise(); Animal cat = new Cat(); cat.makeNoise(); } } // output woof meow Sunday, March 16, 14
  40. 40. Favor Composition Over Inheritance • “HAS-A” can be better than “IS-A” • Eliminates excessive use of subclassing • An object’s behavior can be modified through composition as opposed through inheritance • Allows change in object behavior at run- time 40 Sunday, March 16, 14
  41. 41. Classes Should Be Open for Extension... • ...But Closed for Modification • “Come in,We’re Open” • extend the class to add new behavior • “Sorry,We’re Closed” • the code must remain closed to modification 41 Sunday, March 16, 14
  42. 42. A Simple Hierarchy... 42 Sunday, March 16, 14
  43. 43. ...That Quickly Becomes Complex! 43 Sunday, March 16, 14
  44. 44. Refactored Design 44 Sunday, March 16, 14
  45. 45. Live Demo! 45 Sunday, March 16, 14
  46. 46. Strive for Loosely Coupled Designs... • ...Between Objects That Interact • Allows you to build flexible OO systems that can handle change • interdependency is minimized • Changes to one object won’t affect another object • Objects can be used independently 46 Sunday, March 16, 14
  47. 47. Live Demo! 47 Sunday, March 16, 14
  48. 48. A Class Should Have... • ...Only One Reason to Change • Classes can inadvertently assume too many responsibilities • interdependency is minimized • cross-cutting concerns • Assign a responsibility to one class, and only one class 48 Sunday, March 16, 14
  49. 49. Local C++ User Groups • ACGNJ C++ Users Group • facilitated by Bruce Arnold • acgnj.barnold.us 49 Sunday, March 16, 14
  50. 50. Local Java User Groups (1) • ACGNJ Java Users Group • facilitated by Mike Redlich • javasig.org • Princeton Java Users Group • facilitated byYakov Fain • meetup.com/NJFlex 50 Sunday, March 16, 14
  51. 51. Local Java User Groups (2) • NewYork Java SIG • facilitated by Frank Greco • javasig.com • Capital District Java Developers Network • facilitated by Dan Patsey • cdjdn.com 51 Sunday, March 16, 14
  52. 52. Further Reading 52 Sunday, March 16, 14
  53. 53. 53 Resources •java.sun.com •headfirstlabs.com •themeteorbook.com •eventedmind.com •atmosphere.meteor.com Sunday, March 16, 14
  54. 54. Upcoming Events (1) • Trenton Computer Festival • March 14-15, 2014 • tcf-nj.org • Emerging Technologies for the Enterprise • April 22-23, 2014 • phillyemergingtech.com 54 Sunday, March 16, 14
  55. 55. 55 Upcoming Events (2) Sunday, March 16, 14
  56. 56. 56 Thanks! mike@redlich.net @mpredli javasig.org Sunday, March 16, 14

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