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jgs CSC 308 Software Engineering 1 Lecture 15: Design Patterns - Singleton Dr. Javier Gonzalez-Sanchez [email protected] www.javiergs.com Building 14 -227 Office Hours: By appointment

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jgs Previously …

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 3 Project – User create dots

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 4 Project – User selects Cluster and clicks Run ✅

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 5 Project – User selects Cluster and clicks Run ✅

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 6 Project – User selects Line and clicks Run ✅

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 7 Project – User selects Line and clicks Run ✅

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jgs Solution The Programmer Approach

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 9 Ideas

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jgs Solution The Engineer Approach All about modifiability, extensibility, and reuse

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 11 Ideas

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 12 Think About It Can we do something about that class Repository?

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jgs Singleton Design Patterns

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 14 GoF Patterns

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 15 Singleton

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 16 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 } } } Singleton

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 17 class Singleton{ private static Singleton _instance; // Constructor is 'protected' protected Singleton() {} public static Singleton getInstance(){ if (_instance == null){ _instance = new Singleton(); } return _instance; } } Singleton

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 18 Questions

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 19 Office Hours Tuesday and Thursday 3 - 5 pm But an appointment required Sent me an email – [email protected]

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jgs

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jgs CSC 308 Software Engineering 1 Lab 15: Design Patterns Dr. Javier Gonzalez-Sanchez [email protected] www.javiergs.com Building 14 -227 Office Hours: By appointment

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jgs Javier Gonzalez-Sanchez | CSC 308 | Winter 2023 | 22 Ideas Do you Have Questions About Your Assignment 02?

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jgs CSC 308 Software Engineering I Javier Gonzalez-Sanchez, Ph.D. [email protected] Winter 2023 Copyright. These slides can only be used as study material for the class CSC308 at Cal Poly. They cannot be distributed or used for another purpose.