Polymorphism

Polymorphism concept

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Polymorphism is a fundamental principle in OOP that allows objects of different classes to be treated as objects of a common base class. It enables one interface to be used for different data types or classes, simplifying code and making it more flexible.

Polymorphism allows for methods to behave differently based on the object that invokes them. It enables multiple classes to implement methods that share the same name but provide different functionalities depending on the specific class.

For example, a banking system might have different types of accounts such as SavingsAccount and CheckingAccount. Both types of accounts could share a common method like applyInterest() , but each would calculate interest in a different way.

Bank Account Example:

Imagine we have a base class, BankAccount, and a subclass, SavingsAccount. The method applyInterest() behaves differently in the SavingsAccount class compared to a more generic method in BankAccount:

classDiagram
class BankAccount {
  + deposit(amount)
  + withdraw(amount)
  + getBalance()
} 

class SavingsAccount {
  + Float interestRate
  + applyInterest()
  + withdraw(amount)
}

BankAccount <|-- SavingsAccount

In the diagram:

The method withdraw(amount) is overridden in the SavingsAccount class to account for savings-specific rules (like a fee or limit). Methods within the same class that share the same name but have different parameters.

The method applyInterest() adds behavior specific to savings accounts, demonstrating method overloading because a subclass is providing specific implementation of a method already defined in its superclass.

Polymorphism allows BankAccount and SavingsAccount to share similar methods, but execute them differently depending on the object’s type. For example, both classes have a withdraw(amount) method, but the behavior differs depending on whether the object is a BankAccount or a SavingsAccount.

Why Polymorphism Matters?

Code Reusability

Polymorphism allows a base class like BankAccount to define general behavior, while subclasses like SavingsAccount can build on and modify that behavior. This makes it easier to extend the system without rewriting code.

Maintainability

Polymorphism simplifies code maintenance. If you need to change the behavior of a method for a particular class, you can override it in the subclass, without altering the base class or other subclasses.

Dynamic Behavior

At runtime, the system can decide which method to invoke depending on the object’s type, leading to more flexible and dynamic code.

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Next Step:

Now that you’ve mastered all four core principles of object-oriented programming (OOP), it’s time to explore the Methodologies section, where you can dive into different learning paths. These methodologies provide various ways to apply the OOP concepts you’ve learned based on different teaching styles and use cases.

Quiz

Inheritance