CSE460 Lecture 18

Software Analysis and Design
Additional Design Patterns
(202103)

Transcript

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   CSE 460
   Software Analysis and Design
   Lecture 18: Additional Design Patterns
   Dr. Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   PERALTA 230U
   Office Hours: By appointment
   

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   Announcement
   § Quiz 05 is due tonight. It opens at the end of the lecture
   

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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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   Previously …
   

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    Next
    

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    Chain of Responsibilities, Factory, Adapter
    

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    Chain of Responsibility
    Avoid coupling the sender of a request to its receiver
    by giving more than one object a chance to handle the
    request.
    

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    Chain of Responsibility
    

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    Chain of Responsibility vs Composite vs Decorator
    

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    Chain of Responsibility
    public class Client {
    public static void main(String[] args) {
    // Setup Chain of Responsibility
    ConcreteHandler2 h1 = new ConcreteHandler2();
    ConcreteHandler2 h2 = new ConcreteHandler2();
    ConcreteHandler1 h3 = new ConcreteHandler1();
    h1.setSuccessor(h2);
    h2.setSuccessor(h3);
    // Generate and process request
    int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 };
    for (int i = 0; i < requests.length; i++) {
    h1.HandleRequest(requests[i]);
    }
    }
    }
    

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    Handler
    abstract class Handler {
    public abstract void HandleRequest(int request);
    }
    

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    ConcreteHandler1
    class ConcreteHandler1 extends Handler {
    public void HandleRequest(int request) {
    System.out.println("I am the last in line");
    }
    }
    

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    ConcreteHandler2
    class ConcreteHandler2 extends Handler {
    protected Handler successor;
    public void setSuccessor(Handler successor) {
    this.successor = successor;
    }
    public void HandleRequest(int request) {
    if (request >= 10 && request < 20) {
    // code here
    System.out.println("I am the handling it");
    } else if (successor != null) {
    System.out.println("Passing it...");
    successor.HandleRequest(request);
    }
    }
    }
    

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    Factory
    Wrapper of a constructor
    One entire object to be built in a single method call
    

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    Next
    

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    Abstract Factory
    

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    Products
    public interface Shape {
    void draw();
    }
    public class RoundedRectangle implements Shape {
    public void draw() {
    System.out.println("Inside RoundedRectangle/draw() method.");
    }
    }
    public class RoundedSquare implements Shape {
    public void draw() {
    System.out.println("Inside RoundedSquare/draw() method.");
    }
    }
    public class Rectangle implements Shape {
    public void draw() {
    System.out.println("Inside Rectangle/draw() method.");
    }
    }
    

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    Factories
    public abstract class AbstractFactory {
    Shape getShape(String shapeType) {}
    }
    public class ShapeFactory extends AbstractFactory {
    public Shape getShape(String shapeType){
    if(shapeType.equalsIgnoreCase("RECTANGLE")){
    return new Rectangle();
    }else if(shapeType.equalsIgnoreCase("SQUARE")){
    return new Square();
    }
    return null;
    }
    }
    

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    Factories
    public class RoundedShapeFactory extends AbstractFactory {
    public Shape getShape(String shapeType){
    if(shapeType.equalsIgnoreCase("RECTANGLE")){
    return new RoundedRectangle();
    }else if(shapeType.equalsIgnoreCase("SQUARE")){
    return new RoundedSquare();
    }
    return null;
    }
    }
    

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    Client
    public class Client {
    public static void main(String[] args) {
    AbstractFactory shapeFactory = new ShapeFactory();
    //get an object of Shape Rectangle
    Shape shape1 = shapeFactory.getShape("RECTANGLE");
    //call draw method of Shape Rectangle
    shape1.draw();
    //get an object of Shape Square
    Shape shape2 = shapeFactory.getShape("SQUARE");
    //call draw method of Shape Square
    shape2.draw(); ]
    //get shape factory
    AbstractFactory shapeFactory1 = new RoundedShapeFactory();
    //get an object of Shape Rectangle
    Shape shape3 = shapeFactory1.getShape("RECTANGLE");
    //call draw method of Shape Rectangle
    shape3.draw();
    //get an object of Shape Square
    Shape shape4 = shapeFactory1.getShape("SQUARE");
    //call draw method of Shape Square
    shape4.draw();
    }
    }
    

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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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