Polymorphism (OOP) (OCR A Level Computer Science)

Polymorphism (OOP)

What is Polymorphism?

• Polymorphism is a concept in programming that allows objects to take on different forms or behaviours.

• Different objects can share the same name or behaviour but can work in different ways

• It helps make code more flexible, reusable, and easier to maintain

• It allows flexibility and reusability in programming, making it easier to write and manage code

• Objects can be treated as belonging to a common group, even if they belong to different classes, making your code more versatile and adaptable to changes

Example 1 – Method Overloading

Method Overloading Example 1

• In the example above, all three classes all have a method named move(). Polymorphism allows methods to be declared with the same name but execute different code (in this case printing different messages)

• The override keyword Is used to provide a new implementation for a method that is already defined in the parent class (base class)

Example 2 - Method Overloading

Method Overloading Example 2

• In the above example both the Motorcycle class and the Car class both inherit from the base class 'Cars'

• Objects from the Motorcycle Class and the Car class can call the startEngines() method which will output "Engines Started!"

• If either of the object types call the displayInfo() method, the program will execute the method from the objects class as it overrides the Vehicle class method

• For example

  • If a motorcycle object calls the displayInfo() method, "I am a Motorcycle!" will be output

  • If a Car object calls the displayInfo() method, "I am a Car!" will be output

Treating objects as common groups

• Polymorphism also allows objects of different classes to be treated as objects of a common superclass or base class

• For example:

  • Vehicle vehicle1 = new Car()

  • Vehicle vehicle2 = new Motorcycle()

• This allows an array of type Vehicle to store both Motorcycle and Car objects rather than in separate data structures

  • If the vehicle1.displayInfo() method is called, it will still output "I am a Car!"

  • If the vehicle2.displayInfo() method is called, it will still output "I am a Motorcycle!"

• This flexibility provided by polymorphism are essential for creating more maintainable and modular code