🎯 If you’re preparing OOPS concepts for university exams, here’s a collection of exercises (with increasing difficulty) that touch all the major OOPS concepts in Java. These are highly exam-relevant and will also boost practical understanding 👇

📝 OOPS Practice Exercises in Java (University/College Level)

1️⃣ Classes and Objects

✅ Easy-level, foundation concept

• Write a class Student with attributes: name, rollNumber, and marks.
  Create objects of Student and display their details.

• Create a class Car with properties brand, model, and price.
  Write a method displayInfo() to show car details.

2️⃣ Encapsulation

✅ Testing getters & setters

• Create a class BankAccount with private variables: accountNumber, balance.
  Provide getter and setter methods.
  Write code to deposit money and check balance.

3️⃣ Inheritance

✅ Shows reusability & parent-child relation

• Create a class Person with attributes name, age.
  Derive a subclass Employee with attributes salary and designation.
  Demonstrate inheritance by creating objects.

• Create a base class Shape with method area().
  Extend classes Circle and Rectangle that override area() method.

4️⃣ Polymorphism

✅ Method Overloading & Overriding exercises

• Overloading: Create a class Calculator with methods add(int, int) and add(double, double). Show method overloading.

• Overriding: Create a class Animal with method sound().
  Subclass Dog and Cat to override sound().

5️⃣ Abstraction

✅ Abstract classes practice

• Create an abstract class Vehicle with abstract method start().
  Implement it in subclasses Car and Bike.

6️⃣ Interface

✅ Multiple inheritance via interface

• Create an interface Payment with method pay().
  Implement it in classes CreditCardPayment and UPIPayment.

• Create two interfaces Camera and MusicPlayer.
  Create a class SmartPhone that implements both.

7️⃣ Constructor & ‘this’ keyword

✅ Frequently asked in exams

• Write a program to demonstrate constructor overloading in a Book class.

• Use this keyword to differentiate between class variables and method parameters.

8️⃣ Static Keyword

✅ Important for theory + coding

• Create a class College with static variable collegeName.
  Show how all objects share the same static variable.

• Write a program with a static method displayUniversity() to print a university name.

9️⃣ Real-world Mini Project (Integration of All OOPS)

📌 Often asked as long-answer/15-mark questions

• Design an E-Commerce Application skeleton in Java:

  • Class Product (id, name, price).

  • Class Customer (id, name, email).

  • Abstract class Order with abstract method placeOrder().

  • Subclass OnlineOrder and OfflineOrder that override placeOrder().

  • Interface Payment with pay(). Implement CreditCard and UPI.

  • Demonstrate all OOPS principles in action.

🎯 Why These Are Exam-Ready?

• Covers all four pillars: Encapsulation, Inheritance, Polymorphism, Abstraction.

• Includes syntax-based + application-based questions.

• Gives both small coding snippets (5–8 marks) and long coding problems (10–15 marks).