Procedural vs OOP approach in Java - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of procedural style code

What is the output of this procedural Java code?

Java

public class Main {
    public static void main(String[] args) {
        int a = 5;
        int b = 3;
        int sum = add(a, b);
        System.out.println(sum);
    }

    public static int add(int x, int y) {
        return x + y;
    }
}

A 53

B 8

C Error: method add not found

D 0

💡 Hint

Look at how the add method works and what it returns.

The add method takes two integers and returns their sum. So 5 + 3 = 8.

❓ Predict Output

intermediate

Output of OOP style code

What is the output of this Java code using classes and objects?

Java

class Calculator {
    int a, b;
    Calculator(int a, int b) {
        this.a = a;
        this.b = b;
    }
    int add() {
        return a + b;
    }
}

public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator(5, 3);
        System.out.println(calc.add());
    }
}

A 53

B NullPointerException

C Compilation error: missing return type

D 8

💡 Hint

Check how the add method uses the object's fields.

The Calculator object stores 5 and 3, and add() returns their sum, 8.

🧠 Conceptual

advanced

Difference in data handling between procedural and OOP

Which statement best describes how data is handled differently in procedural vs OOP approaches?

A Both procedural and OOP always keep data and functions separate.

B Procedural code bundles data and functions in objects; OOP separates them completely.

C Procedural code separates data and functions; OOP bundles data and functions together in objects.

D OOP does not use functions, only data.

💡 Hint

Think about how classes group data and behavior.

Procedural programming treats data and functions separately, while OOP groups them inside objects.

🔧 Debug

advanced

Identify the error in this OOP code

What error will this Java code produce?

Java

class Calculator {
    int a, b;
    Calculator(int a, int b) {
        a = a;
        b = b;
    }
    int add() {
        return a + b;
    }
}

public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator(5, 3);
        System.out.println(calc.add());
    }
}

A Output is 0

B Compilation error: variable a not initialized

C NullPointerException at runtime

D Output is 8

💡 Hint

Look at the constructor assignments carefully.

The constructor assigns parameters to themselves, not to the fields. So fields a and b remain 0, sum is 0.

🚀 Application

expert

Choosing approach for a banking system

You need to design a banking system that manages accounts, transactions, and customers. Which approach is best and why?

A OOP, because it models real-world entities like accounts and customers as objects with data and behavior.

B OOP, because it does not allow data to be changed once created.

C Procedural, because it avoids the overhead of creating classes and objects.

D Procedural, because it is simpler and faster for managing many data types separately.

💡 Hint

Think about how real-world things map to programming concepts.

OOP is best for complex systems with entities that have data and behaviors, like accounts and customers.