– Decorator/Composite Dr. Javier Gonzalez-Sanchez [email protected] users.csc.calpoly.edu/~javiergs | javiergs.com Building 14 -227 Office Hours: By appointment
6 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
18 class MainApp { static void main() { // Create ConcreteComponent and two Decorators ConcreteComponent c = new ConcreteComponent(); ConcreteDecoratorA d1 = new ConcreteDecoratorA(); ConcreteDecoratorB d2 = new ConcreteDecoratorB(); // Link decorators d1.SetComponent(c); d2.SetComponent(d1); d2.Operation(); } } Main
20 § Both allow you to change how an object behaves § The decorator pattern can be used to make it possible to extend (decorate) the functionality of a certain object at runtime. § Inheritance adds behavior at compilation-time. Decorator vs Inheritance
30 public class HelperCompanion extends CompanionDecorator { @Override public void doSomething(){ super.doSomething(); System.out.print(" I am here to help you. "); } } HelperCompanion
31 public class AffectiveCompanion extends CompanionDecorator { @Override public void doSomething(){ super.doSomething(); System.out.print(" I am here to cheer you."); } } AffectiveCompanion
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