class Cat extends Animal {   // A Cat "is-a" Animal.

  // The fields `name`, `sound` are inherited from Animal.
  
  // A field specific to cats, not shared by all Animals:
  double clawSharpness;  // 0.0 represents dull; 1.0 is razor-sharp.

  /** Constructor
   * @param _name, the cat's name.
   */
  Cat( String _name ) {
    this.name  = _name;  // BAD --
    this.sound = "meow"; // we're duplicating code from Animal constructor!

    // But this line okay -- it is specific to cats:
    this.clawSharpness = 0.9;  // Kittens start out with sharp claws.
    }

    
  // A method specific to cats, not shared by all Animals:
  /** What happens, when a cat pounces.
   * @return The sound of this cat pouncing.
   */
  String pounce() {
    // Every time they pounce, the claws get 10% closer to perfect sharpness:
    this.clawSharpness += 0.1*(1.0-this.clawSharpness);
    return "whoooomf";
    }
  }