2021-09-22

• ​http://www.plantuml.com/plantuml/png/SoWkIImgAStDuKfCAYufIamkKO02nxpCtCGShioyajIYjCJaLAYmStvEVX66g7jgNafg4HT4Zu9DZQukPq1cEWhV9H-LxvnOmWLK0zGCLvzUoUMI3nS16mpa0qM1Qb54lJDBIbBpkC1k0GdhwO65GKP2N88gvW0K0teH0000

  @startuml
  abstract        Animal
  interface       Color
  interface       Gender
  Animal <|--	Pig
  Animal <|--	Dog
  Animal <|--	Cat
  Pig    <|--	Piggy
  Dog    <|--     Doggy
  Cat    <|--     Kitten
  Color  <|..     Cat
  Gender <|..     Cat
  @enduml
  

• 

public class HelloWorld{

     public static void main(String []args){
        System.out.println("Hello World");
        
        Animal a = new Cat();
        Animal b = new Kitten();
        
        a.who_am_i();
        b.who_am_i();
     }
}

abstract class Animal {
    abstract void who_am_i();
}

class Cat extends Animal {
    void who_am_i() {
        System.out.println("I'm a Cat");
    }
}

class Kitten extends Cat {
    void who_am_i() {
        System.out.println("I'm a Kitten");
    }
}