Copying parent class object into new subclass object

[Wally Hartshorn]

Suppose I have a class (Dog), a subclass (Poodle), and a Dog object that I want to use to create a Poodle object.

One way to do that would be something like this:

public Poodle(Dog dog, String curliness) {
    super(dog.size, dog.color, dog.name, dog.owner, ...etc...);
    this.curliness = curliness;
}

Having to explicitly list all of the fields of the Dog object to set them in the Poodle object feels wrong. Is there a better way to do this?

[Campbell Ritchie]

That shouldn't work if all the fields are correctly labelled private. If there is going to be that sort of copy constructor, it ought to be in the Dog class

public class Dog
{
   public Dog(int size, Color colour, String name, Person owner)
   {
      this.size = size;
      this colour = colour;
      this.name = name;
      this.owner = owner;
   }

   /**
    * Copy constructor . . .
    *@param d etc etc
    */
   public Dog(Dog d)
   {
      this (d.size, d.colour, d.name, d.owner);
   }
}

public class Poodle extends Dog
{
   public Poodle(Dog d, String curliness)
   {
      super(d);
      this.curliness = curliness;
   }
}

You can have other constructors if you wish. You would have to check the design: do you really want a Poodle identical to another Dog in all respects except curliness?