CSE460 Lecture 18

Software Analysis and Design
Additional Design Patterns
(202103)

Transcript

1. jgs 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
2. jgs 460 00010010 Announcement § Quiz 05 is due tonight. It opens at the end of the lecture
3. jgs 460 00010010 Singleton
4. jgs 460 00010010 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 } } }
5. jgs 460 00010010 Singleton class Singleton{ private static Singleton instance; // Constructor is 'protected' protected Singleton() {} public static Singleton getInstance(){ if (instance == null){ instance = new Singleton(); } return instance; } }
6. jgs 460 00010010 Practice
7. jgs 460 00010010 A Singleton
8. jgs 460 00010010 Add More Objects
9. jgs 460 00010010 Previously …
10. jgs 460 00010010 Next
11. jgs 460 00010010 Chain of Responsibilities, Factory, Adapter
12. jgs 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.
13. jgs 460 00010010 Chain of Responsibility
14. jgs 460 00010010 Chain of Responsibility vs Composite vs Decorator
15. jgs 460 00010010 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]); } } }
16. jgs 460 00010010 Handler abstract class Handler { public abstract void HandleRequest(int request); }
17. jgs 460 00010010 ConcreteHandler1 class ConcreteHandler1 extends Handler { public void HandleRequest(int request) { System.out.println("I am the last in line"); } }
18. jgs 460 00010010 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); } } }
19. jgs Factory Wrapper of a constructor One entire object to be built in a single method call
20. jgs 460 00010010 Next
21. jgs 460 00010010 Abstract Factory
22. jgs 460 00010010 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."); } }
23. jgs 460 00010010 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; } }
24. jgs 460 00010010 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; } }
25. jgs 460 00010010 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(); } }
26. jgs 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.