Step by Step solution about How to resolve the algorithm Polymorphic copy step by step in the Kotlin programming language

This Kotlin code defines a simple hierarchy of classes representing animals, with a base class Animal and a derived class Dog. It includes the main function where an instance of Dog is created and copied, and then the copied instance is printed along with the original instance. The code demonstrates polymorphism and object copying in Kotlin.

1. Animal base class:

   • Defines two properties: name (a string) and age (an integer).
   • Provides a default implementation of the copy() function that creates a new instance of Animal with the same name and age.
   • Overrides the toString() function to return a string representation of the animal's name and age.

2. Dog derived class:

   • Inherits from Animal and introduces an additional property breed (a string).
   • Overrides the copy() function to create a new instance of Dog with the same name, age, and breed.
   • Overrides the toString() function to include the breed in the string representation.

3. Main function:

   • Creates an instance of Dog named a with the specified name, age, and breed.
   • Copies the Dog instance a using the copy() function, resulting in a new instance b.
   • Prints the string representations of both a and b using string interpolation.
   • Compares the object identities of a and b using the === operator and prints whether they are the same object or not.

In this code, the copy() function is overridden in the Dog class to create a new instance of Dog with the same properties as the original Dog instance. This is an example of polymorphism, where the behavior of the copy() function changes depending on the runtime type of the object it is called on. Additionally, the code demonstrates object copying by creating a new Dog instance (b) that is a copy of the existing Dog instance (a).

// version 1.1.2

open class Animal(val name: String, var age: Int) {
    open fun copy() = Animal(name, age)
    
    override fun toString() = "Name: $name, Age: $age"     
}   

class Dog(name: String, age: Int, val breed: String) : Animal(name, age) { 
    override fun copy() = Dog(name, age, breed)

    override fun toString() = super.toString() + ", Breed: $breed"
}
          
fun main(args: Array<String>) {
    val a: Animal = Dog("Rover", 3, "Terrier")
    val b: Animal = a.copy()  // calls Dog.copy() because runtime type of 'a' is Dog
    println("Dog 'a' = $a")   // implicitly calls Dog.toString()
    println("Dog 'b' = $b")   // ditto
    println("Dog 'a' is ${if (a === b) "" else "not"} the same object as Dog 'b'")
}