Why object-oriented programming is used in Java - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why use encapsulation in OOP?

Which of the following best explains why encapsulation is used in object-oriented programming?

A To make programs run faster by avoiding method calls

B To allow direct access to all object variables from anywhere

C To hide internal details and protect object data from outside interference

D To write code without using classes or objects

💡 Hint

Think about how encapsulation helps keep data safe inside an object.

Encapsulation hides the internal state of an object and only exposes controlled ways to access or modify it. This protects data and helps maintain integrity.

❓ Predict Output

intermediate

Output of inheritance example

What is the output of this Java code?

Java

class Animal {
    void sound() {
        System.out.println("Some sound");
    }
}
class Dog extends Animal {
    void sound() {
        System.out.println("Bark");
    }
}
public class Main {
    public static void main(String[] args) {
        Animal a = new Dog();
        a.sound();
    }
}

A Some sound

B Bark

C Compilation error

D Runtime error

💡 Hint

Look at which method is called when an Animal reference points to a Dog object.

Even though the reference type is Animal, the actual object is Dog. Java calls the overridden method in Dog, so it prints "Bark".

❓ Predict Output

advanced

Polymorphism with method overloading

What will this Java program print?

Java

class Calculator {
    int add(int a, int b) {
        return a + b;
    }
    int add(int a, int b, int c) {
        return a + b + c;
    }
}
public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator();
        System.out.println(calc.add(2, 3));
        System.out.println(calc.add(1, 2, 3));
    }
}

A Runtime error

B

5
5

C Compilation error due to method overloading

D

5
6

💡 Hint

Check how many arguments each add method takes.

Method overloading allows multiple methods with the same name but different parameters. The calls match the correct method signatures, so outputs are 5 and 6.

🧠 Conceptual

advanced

Why use abstraction in OOP?

Which statement best describes the purpose of abstraction in object-oriented programming?

A To show only essential features and hide complex details from the user

B To allow users to see and modify all internal data of an object

C To make all methods public so they can be accessed anywhere

D To write programs without using any classes

💡 Hint

Think about how abstraction simplifies interaction with objects.

Abstraction hides complex implementation details and shows only what is necessary, making it easier to use and understand objects.

🧠 Conceptual

expert

Main advantage of using OOP in large software projects

What is the main advantage of using object-oriented programming in large software projects?

A It helps organize code into reusable and manageable pieces called objects

B It makes programs run faster by avoiding any use of classes

C It forces all code to be written in a single file for simplicity

D It removes the need for any testing or debugging

💡 Hint

Think about how OOP helps manage complexity in big programs.

OOP organizes code into objects that bundle data and behavior, making large projects easier to maintain, reuse, and understand.