OOP Basics
A blueprint used to create objects in programming.
What is a class?
Output of System.out.println(5 + 3);
✔ Question: What is 8?
A bank app hides account balance details using private variables.
What is encapsulation?
Answer: Error when accessing a private variable outside its class.
Question: What is access violation / compile-time error?
Representing a “Student” with attributes like name and roll number.
Question: What is a class?
An instance created from a class.
Question: What is an object?
Output of System.out.println("Java" + "OOP");
What is JavaOOP?
A child class inherits properties from a parent class.
✔ Question: What is inheritance
Answer: Missing constructor leads to default constructor usage.
✔ Question: What is default constructor?
Creating multiple student records from one blueprint.
✔ Question: What is objects?
A special method automatically invoked when an object is created.
Question: What is a constructor?
Output when a constructor prints “Hello” on object creation.
What is Hello?
Same method name with different parameter lists.
✔ Question: What is method overloading?
Using wrong method signature prevents overriding.
Question: What is method overloading instead of overriding?
Reusing code for “Vehicle → Car → Bike”.
✔ Question: What is inheritance?
Answer: The OOP principle that combines data and methods into one unit.
Question: What is encapsulation?
Output of method overloading call with int parameters selecting int version.
✔ Question: What is calling the int method?
Same method behaves differently based on object type.
✔ Question: What is polymorphism?
Calling parent method explicitly using keyword.
Question: What is super?
Different payment methods (UPI, Card) using same method name.
✔ Question: What is polymorphism?
The keyword used in Java to refer to the current object.
Question: What is this?
Output when overridden method in subclass is called using parent reference.
Question: What is subclass method output (runtime polymorphism)?
Designing a system showing only essential features like ATM interface.
✔ Question: What is abstraction?
Runtime decision of method call based on object type.
Question: What is dynamic binding?
Designing a ride-sharing app using classes and interactions.
Question: What is object-oriented design / OOP principles?