// enumerations/Pet.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.

public class Pet {
  void feed() {}
}

class Dog extends Pet {
  void walk() {}
}

class Fish extends Pet {
  void changeWater() {}
}