CSE 360 Introduction to Software Engineering Lecture 06: Objects and Patterns Dr. Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu | javiergs.com PERALTA 230U Office Hours: By appointment 

Key Ideas CSE360 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 3 Key Concepts Encapsulation Abstraction Hierarchical Relationships Polymorphism Concurrency Persistency 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 4 Abstraction • Reducing by focusing on the essential observable behavior • What will be outside? OOAD, Booch Textbook 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 5 Encapsulation • Hiding the details of the implementation • What is inside? OOAD, Booch Textbook 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 6 Hierarchical Relationships • Creating a hierarchy of abstractions • Who (is a…, uses a…, has a…) ? OOAD, Booch Textbook 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 7 Hierarchical Relationships Association Aggregation Composition Generalization Realization 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 8 8 Hierarchical Relationships 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 9 Polymorphism • The condition of denoting different forms. • A single name may denote objects of many different classes that are related by some common superclass. • When to use it? 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 10 High cohesion Low coupling Important 

Next Step 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 12 The LEGO Paradigm 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 13 Patterns are these Blocks • Design patterns are solutions to software design problems you find again and again in real-world application development. • Patterns are about reusable designs and interactions between objects. • The 23 Gang of Four (GoF) patterns are generally considered the foundation for all other patterns (Gamma, Helm, Johnson, and Vlissides). 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 14 GoF Patterns 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 15 Blueprint 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 16 GoF Patterns 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 17 Observer 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 18 Observer 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 19 Observer Java Listeners 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 20 GoF Patterns 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 21 Decorator 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 22 Examples 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 23 Decorator 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 24 Examples Java UI Objects 

To be continued… Review the code in the slides at the end with examples of Observer and Decorator 

Observer Pattern Example with Java API 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 27 Scenario Observer + update() Observable + addObserver() + notifyObservers() + setChanged() Tutor Student Classroom 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 28 Student import java.util.Observable; import java.util.Observer; public class Student implements Observer { public String answerQuestion (String question) { return "I am thinking about \'" + question +"\'"; } @Override public void update(Observable o, Object arg) { String x = ((Tutor)o).getQuestion(); String y = this.answerQuestion(x); System.out.println(y); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 29 Tutor import java.util.Observable; public class Tutor extends Observable { private String [] questions = { "2 + 2", "public or private", "functional or not fuctional", "white or black" }; private String theQuestion; public void askQuestion() { theQuestion = questions[((int)(Math.random()*10))%4]; setChanged(); notifyObservers(); } public String getQuestion() { return theQuestion; } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 30 Classroom public class Classroom { public static void main(String[] args) { Student student = new Student(); Tutor tutor = new Tutor(); tutor.addObserver(student); for (int i=0; i<5;i++) tutor.askQuestion(); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 31 Output 

Decorator Pattern Example with Java 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 33 Decorator 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 34 Main 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 35 Companion public interface Companion { public void doSomething(); } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 36 BasicCompanion public class BasicCompanion implements Companion { @Override public void doSomething() { System.out.print("Hello Student, "); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 37 CompanionDecorator public class CompanionDecorator implements Companion { protected Companion c; public void add(Companion c){ this.c = c; } @Override public void doSomething() { this.c.doSomething(); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 38 HelperCompanion public class HelperCompanion extends CompanionDecorator { @Override public void doSomething(){ super.doSomething(); System.out.print(" I am here to help you. "); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 39 AffectiveCompanion public class AffectiveCompanion extends CompanionDecorator { @Override public void doSomething(){ super.doSomething(); System.out.print(" I am here to cheer you."); } } 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 40 Homework Complete This Week’s Hybrid Activities 

Javier Gonzalez-Sanchez | CSE360 | Fall 2020 | 41 References Chapter 5 

CSE360 – Introduction to Software Engineering Javier Gonzalez-Sanchez [email protected] Fall 2020 Disclaimer. These slides can only be used as study material for the class CSE360 at ASU. They cannot be distributed or used for another purpose.