A cliché example of interface vs. abstract class in Java

InterfaceAbstractClass.java

// Behavior of talking
interface Talks {
  void talk(String what);
}

// Behavior of making sound
interface MakesSound {
  void makeSound(String what);
}

// Behavior of moving
interface Moves {
  void move(String where);
}

// Abstract type of an organism which has a name and can describe itself
abstract class Organism {
  public String name;

  public abstract String describe();
}

// Abstract type of an animal which is an organism, which has a kind, which can describe itself, make sound and move
abstract class Animal extends Organism implements MakesSound, Moves {
  public String kind;
}

// Abstract type of a person which is an organism, who has an age, who can describe himself/herself, talk and move
abstract class Person extends Organism implements Talks, Moves {
  public int age;
}

// Concerete type for a cat which is an animal -therefore an organism-, which can describe itself, make sound and move
class Cat extends Animal {
  public Cat(String name, String kind) {
    this.name = name;
    this.kind = kind;
  }

  @Override public String describe() {
    return kind + " cat named " + name;
  }

  @Override public void makeSound(String what) {
    System.out.println(describe() " meows " + what);
  }

  @Override public void move(String where) {
    System.out.println(describe() + " moves to " + where);
  }
}

// Concerete type for a doctor which is a person -therefore an organism-, who has an age, who can describe himself/herself, talk and move
class Doctor extends Person {
  public Doctor(String name, int age) {
    this.name = name;
    this.age = age;
  }

  @Override public String describe() {
    return "" + age + " year(s) old doctor named " + name;
  }

  @Override public void talk(String what) {
    System.out.println(describe() " talks and says " + what);
  }

  @Override public void move(String where) {
    System.out.println(describe() + " moves to " + where);
  }
}