CSE360 Introduction to Software Engineering Lecture: Singleton Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu Office Hours: By appointment 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 2 Project 02 • User can draw dots on the Screen • User select Cluster or Line Box • User click the “Run” button • Computer Calculate either o A line that connect all dots using the “nearest neighbor” algorithm o Divide the dots in TWO groups (clusters). Some dots became red, and others became blue –team Blue and team Red • Show results on the screen 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 3 Second Draft 

Singleton 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 5 GoF Patterns Creational Patterns • Abstract Factory • Builder • Factory Method • Prototype • Singleton Structural Patterns • Adapter • Bridge • Composite • Decorator • Façade • Flyweight • Proxy Behavioral Patterns • Chain of Responsibility • Command • Interpreter • Iterator • Mediator • Memento • Observer • State • Strategy • Template Method • Visitor 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 6 Singleton 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 7 Singleton class MainApp { public static void Main(String []a){ // Constructor is protected -- cannot use new Singleton s1 = Singleton.getInstance(); Singleton s2 = Singleton.getInstance(); // Test for same instance if (s1 == s2){ // true - Objects are the same instance } } } 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 8 Singleton class Singleton{ private static Singleton _instance; // Constructor is 'protected' private Singleton() {} public static Singleton getInstance(){ if (_instance == null){ _instance = new Singleton(); } return _instance; } } 

Connecting the Dots SOLID Principles 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 10 Connecting the Dots 

Javier Gonzalez-Sanchez | CSE360 | Summer 2018 | 11 Homework • Draft of Project 02 is due Monday before our lecture. • The midterm exam will be Tuesday instead of Monday. • The final version of Project 02 is due Monday midnight. I will answer questions during the lecture on Monday. • A correct solution is not only a solution that “compiles and runs”; but a solution that matches the design we have agreed on. 

CSE360 – Introduction to Software Engineering Javier Gonzalez-Sanchez [email protected] Summer 2022 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.