What is encapsulation in object-oriented programming?

What is encapsulation in object-oriented programming?

• A. Encapsulation bundles data and methods in a class and hides internal state with access control
• B. Inheritance models is-a relationships via subclassing
• C. Polymorphism allows different types to be treated uniformly
• D. Abstraction hides complexity by exposing essential features

Answer: (A)

Encapsulation is about bundling the data and the methods that operate on that data into a single unit and controlling access to the inner state. In a class, fields are typically kept private and exposed only through public methods, so external code can interact with the object through a well-defined interface rather than touching its internal representation directly. This protects invariants and makes the object easier to use safely. For example, a BankAccount might store its balance privately and offer deposit and withdraw methods, ensuring money can’t be set to an invalid value from outside the class. This approach also makes it possible to change how data is stored internally without breaking code that uses the class, as long as the public behavior stays consistent. The other concepts describe different ideas: inheritance is about creating new classes from existing ones, polymorphism lets different types be treated through a common interface, and abstraction focuses on hiding unnecessary details and exposing essential features. While related, they don’t define encapsulation—the act of hiding internal state and exposing a controlled interface.

Encapsulation is about bundling the data and the methods that operate on that data into a single unit and controlling access to the inner state. In a class, fields are typically kept private and exposed only through public methods, so external code can interact with the object through a well-defined interface rather than touching its internal representation directly. This protects invariants and makes the object easier to use safely. For example, a BankAccount might store its balance privately and offer deposit and withdraw methods, ensuring money can’t be set to an invalid value from outside the class.

This approach also makes it possible to change how data is stored internally without breaking code that uses the class, as long as the public behavior stays consistent.

The other concepts describe different ideas: inheritance is about creating new classes from existing ones, polymorphism lets different types be treated through a common interface, and abstraction focuses on hiding unnecessary details and exposing essential features. While related, they don’t define encapsulation—the act of hiding internal state and exposing a controlled interface.