Question 1

What is the difference between method overloading and method overriding?

Accepted Answer

Overloading defines multiple methods with the same name but different parameters (same class); overriding provides a new implementation in a subclass. Overloading = compile-time polymorphism (same class, different signatures). Overriding = runtime polymorphism (subclass redefines parent method with same signature). Both enable 'same name, different behavior'.

Question 2

What is the difference between an abstract class and an interface?

Accepted Answer

Abstract class can have state and method implementations; an interface (classically) only declares method signatures, enabling multiple inheritance. Abstract class: can have fields, constructors, and concrete methods. Interface: defines a contract (methods without bodies). A class can implement multiple interfaces but extend only one class.

Question 3

What is the Singleton design pattern?

Accepted Answer

Ensures a class has only one instance and provides a global access point to it. Singleton restricts instantiation to one object. Common uses: database connection pool, configuration manager, logger. Implemented by making the constructor private and providing a static getInstance() method.

Question 4

What does SOLID stand for in software engineering?

Accepted Answer

Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion. SOLID: S = one reason to change; O = open to extend, closed to modify; L = subclasses substitutable for parent; I = prefer small specific interfaces; D = depend on abstractions, not concretions.

Question 5

What is coupling in object-oriented design?

Accepted Answer

The degree of dependency between classes — low coupling is preferred for maintainability and testability. High coupling means classes are tightly dependent — a change in one breaks others. Low coupling means classes are independent, making code easier to test, maintain, and extend.

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