Scala - Inheritance and polymorphism

Category : Scala | Sub Category : Scala Programs | By Prasad Bonam Last updated: 2023-10-21 03:27:41 Viewed : 564

In Scala, inheritance and polymorphism work similarly to other object-oriented programming languages, allowing classes to inherit fields and methods from other classes and enabling the use of polymorphic behavior through method overriding. Here is an overview of inheritance and polymorphism in Scala:

1. Inheritance:

   • Inheritance allows a class to inherit properties and behaviors from another class, known as the superclass or base class.
   • In Scala, classes can inherit from only one superclass, but they can mix in multiple traits, which are similar to interfaces in other languages.
   • The extends keyword is used to declare that one class extends another.
   • Example of inheritance in Scala:

   scalaCopy code
   class Animal(val name: String) {
       def sound(): String = "Some sound"
   }
   
   class Dog(name: String) extends Animal(name) {
       override def sound(): String = "Woof"
   }
   

2. Polymorphism:

   • Polymorphism allows objects of different types to be treated as objects of a common superclass.
   • Method overriding enables a subclass to provide a specific implementation of a method that is already defined in its superclass.
   • In Scala, the override keyword is used to indicate that a method is being overridden.
   • Example of polymorphism in Scala:

   scalaCopy code
   val animal: Animal = new Dog("Buddy")
   println(animal.sound()) // Output: "Woof"
   

In these examples, the first one demonstrates inheritance with the Animal and Dog classes, where the Dog class extends the Animal class and overrides the sound method. The second example illustrates polymorphism, where an instance of the Dog class is assigned to a variable of type Animal, demonstrating that a subclass instance can be treated as an instance of its superclass.

inheritance and polymorphism with examples and corresponding outputs in Scala.

Example of Inheritance:

scalaCopy code
class Animal(val name: String) {
  def sound(): String = "Some sound"
}

class Dog(name: String) extends Animal(name) {
  override def sound(): String = "Woof"
}

// Creating instances of Animal and Dog
val animal = new Animal("Generic Animal")
val dog = new Dog("Buddy")

// Calling the sound method for both instances
println(animal.sound()) // Output: "Some sound"
println(dog.sound()) // Output: "Woof"

In this example, we have an Animal class with a method sound and a Dog class that extends the Animal class. The sound method is overridden in the Dog class to return "Woof". When we create instances of Animal and Dog and call the sound method, we get the respective outputs.

Example of Polymorphism:

scalaCopy code
class Animal(val name: String) {
  def sound(): String = "Some sound"
}

class Dog(name: String) extends Animal(name) {
  override def sound(): String = "Woof"
}

// Polymorphism example
val animal: Animal = new Dog("Buddy")
println(animal.sound()) // Output: "Woof"

In this example, we have an Animal class and a Dog class that extends the Animal class. We create an instance of Dog and assign it to a variable of type Animal. Even though the variable is of type Animal, it holds an instance of Dog. When we call the sound method using the animal variable, it invokes the overridden method from the Dog class, demonstrating polymorphic behavior.

These examples illustrate how inheritance and polymorphism work in Scala, showcasing the relationship between superclass and subclass, and the ability to treat objects of different types as instances of a common superclass.