CODEWITHSUNDEEP
javaoopcopy-constructor
TomTom
TomTom

Reputation: 2930

Copy an object that contains a super class of another object

I would like to create a copy of an object that contains a super class of another object. In this example I want to make a copy of the Box that contains a Toy. But all kind of toys can be in the box. What would be the best way to create the copy constructor in Toy?

class Box {
    Toy toy;
    public Box(Toy toy) {
        this.toy = toy;
    }
    public Box(Box box) {
        this.toy = new Toy(box.getToy());
    }
}
abstract class Toy {
    public Toy(String name) {
        // ...
    }
}   
class Car extends Toy {
    public Car(String name) {
        super(name);
        // ...
    }
}
class Puppet extends Toy {
    public Puppet(String name) {
        super(name);
        // ...
    }
}

I don't really have an idea how to approach this problem.

Upvotes: 1

Views: 158

Answers (3)

Mohammadreza Khatami
Mohammadreza Khatami

Reputation: 1332

i think this structure can help you to have an idea,in this case we pass an Object toy using Box Constructor to SuperClass(Toy) and in Toy Class we have a Constructor to Accept an Object from Toy Class then it's call getInstance Method for Initialize toy object(just for example).

class Box extends Toy
{
  public Box(Toy toy) 
  {
     super(toy);
  }
}
Class Toy
{
   private static Toy toys = new Toy();
   Toy(){}
   Toy(Toy toy)
   {
      toy = Toy.getInstance();
   }
   public static Toy getInstance()
   {
     return toys;
   }
}

and either,if you don't want other Classes(sub class) to don't see a specified methods and attributes just make them private,and if you want sub classes haven't access to set and get methods too,make them private only!

Upvotes: 0

Paul Boddington
Paul Boddington

Reputation: 37645

Make Toy have an abstract method copy() with return type Toy. Then you will be forced to override this in Car and Puppet. In the copy constructor for Box you can use box.getToy().copy().

Upvotes: 6

Dici
Dici

Reputation: 25950

You can override the clone method of each Toy's subclass and then :

public Box(Box box) {
    this.toy = (Toy) box.getToy().clone();
}

Alternatively, if you have a constant number of types of toy, you can use an enumeration instead of a class.

Upvotes: 1

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