CSE564 Lecture 18

Software Design
Additional Patterns II
(202111)

Transcript

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   CSE 564
   Software Design
   Lecture 18: More Patterns II
   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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   The System
   D
   B
   A
   C
   D
   B
   A
   C
   Clustering
   TSP -Nearest Neighbor
   

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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
   // Setup Chain of Responsibility
   Handler h1 = new ConcreteHandler1();
   Handler h2 = new ConcreteHandler2();
   Handler h3 = new ConcreteHandler3();
   h1.SetSuccessor(h2);
   h2.SetSuccessor(h3);
   // Generate and process request
   int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 };
   foreach (int i=0; ih1.HandleRequest(request[i]);
   }
   

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   Handler
   abstract class Handler {
   protected Handler successor;
   public void setSuccessor(Handler successor) {
   this.successor = successor;
   }
   public abstract void HandleRequest(int request);
   }
   

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   ConcreteHandler
   class ConcreteHandler1 extends Handler {
   public override void HandleRequest(int request) {
   if (request >= 0 && request < 10) {
   // code here…
   } else if (successor != null) {
   successor.HandleRequest(request);
   }
   }
   }
   class ConcreteHandler2 extends Handler {
   public override void HandleRequest(int request) {
   if (request >= 10 && request < 20) {
   // code here
   } else if (successor != null) {
   successor.HandleRequest(request);
   }
   }
   }
   

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   Chain of Responsibility vs Composite vs Decorator
   

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    Strategy
    Define a family of algorithms, encapsulate each one,
    and make them interchangeable
    

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    Strategy
    

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    Strategy
    Context context;
    // Three contexts following different strategies
    context = new Context(new ConcreteStrategyA());
    context.ContextInterface();
    context = new Context(new ConcreteStrategyB());
    context.ContextInterface();
    context = new Context(new ConcreteStrategyC());
    context.ContextInterface();
    

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    Composite
    Compose objects into tree structures to represent
    part-whole hierarchies. Composite lets clients treat
    individual objects and compositions of objects
    uniformly
    

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    Composite
    

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    564 00010010
    Composite vs Decorator
    § The difference is more one of purpose than implementation
    

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    564 00010010
    Create a Tree Structure
    Composite root = new Composite("root");
    root.Add(new Leaf("Leaf A"));
    root.Add(new Leaf("Leaf B"));
    Composite comp = new Composite("Composite X");
    comp.Add(new Leaf("Leaf XA"));
    comp.Add(new Leaf("Leaf XB"));
    root.Add(comp);
    root.Add(new Leaf("Leaf C"));
    // Add and remove a leaf
    Leaf leaf = new Leaf("Leaf D");
    root.Add(leaf);
    root.Remove(leaf);
    // Recursively display tree
    root.Display(1);
    

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    Adapter
    Convert the interface of a class into another interface
    clients expect
    

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    Adapter
    

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    Example
    RectangleAdapter
    + draw
    Rectangle
    + draw
    + draw
    

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    Client
    public class Client {
    public static void main(String[] args) {
    Shape shape = new RectangleAdapter(new Rectangle();
    int x1 = 10, y1 = 20;
    int x2 = 30, y2 = 60;
    shape.draw(x1, y1, x2, y2);
    }
    }
    

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    Adapter
    class RectangleAdapter implements Shape {
    private Rectangle adaptee;
    public RectangleAdapter(Rectangle rectangle) {
    this.adaptee = rectangle;
    }
    public void draw(int x1, int y1, int x2, int y2) {
    int x = Math.min(x1, x2);
    int y = Math.min(y1, y2);
    int width = Math.abs(x2 - x1);
    int height = Math.abs(y2 - y1);
    adaptee.draw(x, y, width, height);
    }
    }
    

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    Adaptee
    class Rectangle {
    public void draw(int x, int y, int width, int height) {
    System.out.println("Rectangle with coordinate left-down point”);
    }
    }
    

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    Bridge
    Decouple an abstraction from its implementation so
    that the two can vary independently.
    

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    Bridge
    

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    Bridge
    Abstraction ab = new RefinedAbstraction();
    // Set implementation and call
    ab.setImplementor (new ConcreteImplementorA() );
    ab.Operation();
    // Change implemention and call
    ab.setImplementor (new ConcreteImplementorB() );
    ab.Operation();
    

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    Strategy vs Bridge
    

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    Strategy vs Bridge
    Bridge Pattern makes a distinction
    between an abstraction and an
    implementation in such a way that the
    two can vary independently
    Car - Engine
    changing the behavior
    of an object at run
    time.
    Game: Weapons
    

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    Questions
    

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    CSE 564 Software Design
    Javier Gonzalez-Sanchez, Ph.D.
    javiergs@asu.edu
    Fall 2021
    Copyright. These slides can only be used as study material for the class CSE564 at ASU.
    They cannot be distributed or used for another purpose.
    

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