Ruby

Inheritance

class Car
  def fast
    "Cars are fast!"
  end
end

class ElectricCar < Car
  def fast
    super + " but an electric car can accelerate faster!"
  end
end

tesla = ElectricCar.new
puts tesla.fast

class Car
  def runs_on(name, fuel)
    "#{name} runs on #{fuel}."
  end
end

class PetrolCar < Car
  def runs_on(name, fuel)
    super
  end
end

ferrari = PetrolCar.new
puts ferrari.runs_on("Ferrari", "petrol")

class Car
  def runs_on(fuel)
    "Your car runs on #{fuel}."
  end
end

class ElectricCar < Car
  def runs_on
    super("battery")
  end
end

tesla = ElectricCar.new
puts tesla.runs_on