CSE460 Lecture 17

Software Analysis and Design
Singleton
(202103)

Transcript

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   CSE 460
   Software Analysis and Design
   Lecture 17: Singleton
   Dr. Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   PERALTA 230U
   Office Hours: By appointment
   

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   Previously …
   

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   Practice
   

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   Observer Pattern
   

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   Decorator Pattern
   

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   Solution: UI + Observer + Decorator
   

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   Let us Continue the Practice
   

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   GoF Patterns
   

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   Singleton
   

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    Singleton
    A B
    

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    Singleton
    A B
    Printer
    DataBaseConnection
    UniversityPresident
    Pacman
    Logger
    ControlCenter
    

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    Singleton
    

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    Singleton
    class Main {
    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
    }
    }
    }
    

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    Singleton
    class Singleton{
    private static Singleton instance;
    // Constructor is 'protected'
    protected Singleton() {}
    public static Singleton getInstance(){
    if (instance == null){
    instance = new Singleton();
    }
    return instance;
    }
    }
    

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    Practice
    

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    A Singleton
    

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    Add More Objects
    

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    CSE 460 Software Analysis and Design
    Javier Gonzalez-Sanchez
    javiergs@asu.edu
    Fall 2020
    Disclaimer. These slides can only be used as study material for the class CSE460 at ASU. They cannot be distributed or used for another purpose.
    

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