What are the four fundamental pillars of object-oriented programming, and can you give a simple example for each?

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Accepted Answer

The four fundamental pillars of object-oriented programming are encapsulation, inheritance, polymorphism, and abstraction.

First, encapsulation. This is the principle of bundling data and the methods that manipulate that data into a single unit called a class. Internal data is protected by making it private, and public methods are exposed to access it. For example, a BankAccount class might have a private balance attribute and public deposit and withdraw methods.

Second, inheritance. This allows a class to inherit properties and methods from another class. The child class extends the parent class. For example, a Car class can inherit from a Vehicle class and reuse its start method while adding its own attributes like numberOfDoors.

Third, polymorphism. This is the ability of an object to take multiple forms. The same method can behave differently depending on which object calls it. For example, a calculateArea method can return different results for a Circle and a Rectangle, but both can be called in the same way.

Fourth, abstraction. This consists of hiding complex implementation details and exposing only the essentials. For example, a Payment interface can define a processPayment method without specifying how each payment type implements it.

These four concepts work together to create modular, reusable, and maintainable code.