Question

I need to create class Dog and PurebredDog extending Dog. Problem is that Dog can be at once single object and array of objects (Dogs and PurebreedDogs :

 Dog pack[]={new Dog(76589,"As","black",18,
                    "Ann","Kowalsky"),
           new PurebreedDog(45321,"Labrador","Elf","black",25, 
                          "Angus","Mati","Barbara","Smith"),
           new Dog(102467,"Gamma","brown",89,
                    "Josh","Coke"),
            new PurebreedDog(9678,"York","Theta","brown",8,
                    "Emka","Figaro","Alice","Cat")};    

for(int i=0; i < pack.length; i++)
  System.out.println(pack[i]+"\n\n");

How to write proper constructor for Dog ?
You could do :

public Dog(String name, etc){
}

but how to write constructor for array of dogs ?

public Dog(Dog[]tab) ?

And then how to recall it’s elements ? Is pack[] a 2d array ?

Answer 1

To simplify things, an instance of Dog really should refer to a single Dog. So your constructor should look similar to (the data types are just examples):

Dog(int ID, String color, String name, ...)

PurebreedDog would subclass Dog and provide any additional constructor parameters (and members) such as breed, etc.

To deal with multiple dogs, I recommend you store instances of the class in a List, HashTable, or other type of data structure that is designed to hold multiple elements. The actual structure you use will depend upon your requirements.