Example of composition usage in Java 7 & 8 insead of JavaScript. Follow up to: https://www.youtube.com/watch?v=wfMtDGfHWpA

composition-java7-lombok-example.bash

javac CompositionJava7LombokExample.java -cp ~/.m2/repository/org/projectlombok/lombok/1.16.6/lombok-1.16.6.jar
java -cp ./ Main
# Bark, Bark!
# Driving to the destination...
# What a day! What a lovely day!
# What a day! What a lovely day!
# Bark, Bark!
# Bark, Bark!

composition-java8-example.bash

/usr/lib/jvm/java-8-oracle/bin/javac CompositionJava8Example.java 
/usr/lib/jvm/java-8-oracle/bin/java -cp ./ Main 
# Bark, Bark!
# Driving to the destination...
# What a day! What a lovely day!
# What a day! What a lovely day!
# Bark, Bark!
# Bark, Bark!

CompositionJava7LombokExample.java

import lombok.Delegate;

interface Barker {
  void bark();

  class DefaultImpl implements Barker {
    @Override
    public void bark() {
      System.out.println("Bark, Bark!");
    }
  }
}
interface Pooper {
  void poop();

  class DefaultImpl implements Pooper {
    @Override
    public void poop() {
      System.out.println("<dump droped>");
    }
  }
}
interface Meower {
  void meow();

  class DefaultImpl implements Meower {
    @Override
    public void meow() {
      System.out.println("Meow!");
    }
  }
}
interface Cleaner {
  void clean();

  class DefaultImpl implements Cleaner {
    @Override
    public void clean() {
      System.out.println("Cleaning for effect...");
    }
  }
}
interface Driver {
  void drive();

  class DefaultImpl implements Driver {
    @Override
    public void drive() {
      System.out.println("Driving to the destination...");
    }
  }
}
interface Killer {
  void kill();

  class DefaultImpl implements Killer {
    @Override
    public void kill() {
      System.out.println("What a day! What a lovely day!");
    }
  }
}


class Dog implements Barker, Pooper {
  @Delegate
  private Barker barker = new Barker.DefaultImpl();
  @Delegate
  private Pooper pooper = new Pooper.DefaultImpl(); 
}
class Cat implements Meower, Pooper {
  @Delegate
  private Pooper pooper = new Pooper.DefaultImpl();
  @Delegate
  private Meower meower = new Meower.DefaultImpl();
}
class CleaningRobot implements Driver, Cleaner {
  @Delegate
  private Driver driver = new Driver.DefaultImpl();
  @Delegate
  private Cleaner cleaner = new Cleaner.DefaultImpl();
}
class MurderRobot implements Driver, Killer {
  @Delegate
  private Driver driver = new Driver.DefaultImpl();
  @Delegate
  private Killer killer = new Killer.DefaultImpl();
}
class MurderRobotDog implements Driver, Killer, Barker {
  @Delegate
  private Driver driver = new Driver.DefaultImpl();
  @Delegate
  private Barker barker = new Barker.DefaultImpl();
  @Delegate
  private Killer killer = new Killer.DefaultImpl();
}
class Main {
  public static void main(String[] args) {
    MurderRobotDog mrd = new MurderRobotDog();
    mrd.bark();
    mrd.drive();
    mrd.kill();
    
    Killer killer = mrd;
    killer.kill();

    Barker barker = mrd;
    barker.bark();
    barker = new Dog();    
    barker.bark();
  }
}

CompositionJava8Example.java

interface Barker {
  default void bark() {
    System.out.println("Bark, Bark!");
  }
}
interface Pooper {
  default void poop() {
    System.out.println("<dump droped>");
  }
}
interface Meower {
  default void meow() {
    System.out.println("Meow!");
  }
}
interface Driver {
  default void drive() {
    System.out.println("Driving to the destination...");
  }
}
interface Cleaner {
  default void clean() {
    System.out.println("Cleaning for effect...");
  }
}
interface Killer {
  default void kill() {
    System.out.println("What a day! What a lovely day!");
  }
}

class Dog implements Barker, Pooper {
  
}
class Cat implements Meower, Pooper {
  
}
class CleaningRobot implements Driver, Cleaner {
  
}
class MurderRobot implements Driver, Killer {
  
}
class MurderRobotDog implements Driver, Killer, Barker {
  
}
class Main {
  public static void main(String[] args) {
    MurderRobotDog mrd = new MurderRobotDog();
    mrd.bark();
    mrd.drive();
    mrd.kill();
    
    Killer killer = mrd;
    killer.kill();

    Barker barker = mrd;
    barker.bark();
    barker = new Dog();    
    barker.bark();
  }
}