Procedural vs OOP approach in Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a procedural method that prints a greeting.

Java

public class Greeting {
    public static void [1]() {
        System.out.println("Hello, world!");
    }
}

Drag options to blanks, or click blank then click option'

Amain

Bgreet

Cprint

Dhello

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'main' instead of a custom method name.

Using 'print' which is not defined here.

The method name should be greet to match the call in procedural style.

2fill in blank

medium

Complete the code to create an object of class Person and call its method.

Java

public class Person {
    public void sayHello() {
        System.out.println("Hi!");
    }

    public static void main(String[] args) {
        Person p = new [1]();
        p.sayHello();
    }
}

Drag options to blanks, or click blank then click option'

APerson

BHuman

CObject

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different class name like 'Human' or 'Object' which is incorrect here.

To create an object of the class Person, you use new Person().

3fill in blank

hard

Fix the error in the procedural code by completing the method call.

Java

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

    public static void main(String[] args) {
        int result = Calculator.[1](5, 3);
        System.out.println(result);
    }
}

Drag options to blanks, or click blank then click option'

Aplus

Bsum

Cadd

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names not defined like 'sum' or 'plus'.

The method defined is named add, so the call must use add.

4fill in blank

hard

Fill both blanks to complete the OOP class with a constructor and a method call.

Java

public class Car {
    private String model;

    public [1](String model) {
        this.model = model;
    }

    public void displayModel() {
        System.out.println("Model: " + [2]);
    }
}

Drag options to blanks, or click blank then click option'

ACar

Bmodel

Cthis.model

DdisplayModel

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different constructor name.

Using just 'model' instead of 'this.model' inside the method.

The constructor name must match the class name Car, and to access the instance variable inside the method, use this.model.

5fill in blank

hard

Fill all three blanks to create an object, call a method, and print the result.

Java

public class Rectangle {
    private int width;
    private int height;

    public Rectangle(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public int area() {
        return width * height;
    }

    public static void main(String[] args) {
        Rectangle [1] = new Rectangle(4, 5);
        int [2] = [1].area();
        System.out.println([2]);
    }
}

Drag options to blanks, or click blank then click option'

Arect

Bresult

Darea

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same variable name for object and result.

Not calling the method correctly.

We create an object named rect, store the area in result, and print rect.

Practice

1. Which statement best describes the procedural programming approach in Java?

easy

A. It focuses on graphical user interfaces.

B. It models real-world things as objects with data and actions.

C. It uses inheritance and polymorphism only.

D. It writes step-by-step instructions to perform tasks.

Solution

1. Step 1: Understand procedural programming basics

   Procedural programming focuses on writing instructions in order to perform tasks.

2. Step 2: Compare with other approaches

   OOP models real-world things as objects, which is different from procedural step-by-step instructions.

3. Final Answer:

   It writes step-by-step instructions to perform tasks. -> Option D

4. Quick Check:

   Procedural = step-by-step instructions [OK]

Hint: Procedural = step-by-step instructions, not objects [OK]

Common Mistakes:

• Confusing procedural with object-oriented concepts
• Thinking procedural uses objects
• Assuming procedural focuses on GUIs

2. Which of the following is the correct way to define a class in Java using OOP?

easy

A. class Car { int speed; void drive() { } }

B. procedure Car { speed = 0; drive() }

C. function Car() { speed = 0; drive() }

D. object Car = { speed: 0, drive: function() {} }

Solution

1. Step 1: Identify Java class syntax

   Java classes are defined using the keyword 'class' followed by the class name and curly braces.

2. Step 2: Check options for correct Java syntax

   class Car { int speed; void drive() { } } uses 'class' keyword and proper Java method and variable syntax.

3. Final Answer:

   class Car { int speed; void drive() { } } -> Option A

4. Quick Check:

   Java class syntax uses 'class' keyword [OK]

Hint: Java classes start with 'class' keyword and curly braces [OK]

Common Mistakes:

• Using 'procedure' or 'function' keywords which are not Java syntax
• Using object literal syntax like JavaScript
• Missing curly braces or semicolons

3. What will be the output of this Java code using procedural style?

int speed = 0;
speed = speed + 10;
System.out.println(speed);

medium

A. speed

B. 0

C. 10

D. Compilation error

Solution

1. Step 1: Trace variable assignment

   Initially, speed = 0. Then speed = speed + 10 sets speed to 10.

2. Step 2: Print the value of speed

   System.out.println(speed) prints the current value, which is 10.

3. Final Answer:

   10 -> Option C

4. Quick Check:

   speed updated to 10, printed 10 [OK]

Hint: Follow variable changes step-by-step to find output [OK]

Common Mistakes:

• Thinking output is variable name instead of value
• Assuming initial value prints without update
• Confusing syntax causing errors

4. Identify the error in this OOP Java code snippet:

class Dog {
  String name;
  void bark() {
    System.out.println(name + " barks");
  }

  public static void main(String[] args) {
    Dog d = new Dog();
    d.bark();
  }
}

medium

A. Cannot call method bark() without static keyword

B. Missing constructor to set name

C. Variable name is not declared

D. No error, code runs fine

Solution

1. Step 1: Check object initialization

   Dog object 'd' is created but 'name' is never set, so it is null.

2. Step 2: Understand effect of missing constructor

   Without setting 'name', bark() prints 'null barks', which may be unintended. Adding a constructor to set 'name' fixes this.

3. Final Answer:

   Missing constructor to set name -> Option B

4. Quick Check:

   Object fields need initialization [OK]

Hint: Uninitialized fields cause null or default values [OK]

Common Mistakes:

• Thinking bark() must be static
• Assuming variable 'name' is undeclared
• Ignoring that code compiles but may print null

5. You want to create a program to manage a library system with books and members. Which approach is best and why?

hard

A. OOP, because it models books and members as objects with properties and actions

B. Procedural, because it uses less memory

C. Procedural, because it is simpler for large systems

D. OOP, because it avoids using classes

Solution

1. Step 1: Analyze program needs

   A library system has entities like books and members with data and behaviors.

2. Step 2: Choose approach based on modeling

   OOP models real-world entities as objects, making it easier to manage complex data and actions.

3. Final Answer:

   OOP, because it models books and members as objects with properties and actions -> Option A

4. Quick Check:

   Complex systems benefit from OOP modeling [OK]

Hint: Use OOP for real-world entities with data and actions [OK]

Common Mistakes:

• Choosing procedural for complex object management
• Thinking OOP avoids classes (it uses them)
• Assuming procedural always uses less memory