Visibility modifiers (public, private, internal, protected) in Kotlin - Mini Project: Build & Apply

Visibility modifiers (public, private, internal, protected)

📖 Scenario: You are creating a simple Kotlin class to understand how different visibility modifiers control access to class members.

🎯 Goal: Build a Kotlin class with properties and functions using public, private, internal, and protected visibility modifiers and observe how they affect access.

📋 What You'll Learn

Create a Kotlin class named Car with properties and functions using all four visibility modifiers.

Add a variable to hold the car's brand with public visibility.

Add a variable to hold the car's engine number with private visibility.

Add a function with internal visibility that returns the car's brand.

Add a protected function that returns the engine number.

Create a subclass SportsCar that tries to access the protected function.

Print outputs to show which members are accessible.

💡 Why This Matters

🌍 Real World

Visibility modifiers help protect sensitive data and control how parts of your code can be used or changed by others.

💼 Career

Understanding visibility is essential for writing safe, maintainable Kotlin code in professional Android or backend development.

1

Create the Car class with public and private properties

Create a Kotlin class called Car. Inside it, declare a public variable brand of type String and set it to "Toyota". Also declare a private variable engineNumber of type String and set it to "ENG12345".

Kotlin

class Car {
    // Your code here
}

Need a hint?

Use val brand: String = "Toyota" and private val engineNumber: String = "ENG12345" inside the class.

2

Add an internal function to get the brand

Inside the Car class, add an internal function called getBrand that returns the brand variable.

Kotlin

class Car {
    val brand: String = "Toyota"
    private val engineNumber: String = "ENG12345"

    // Your code here
}

Need a hint?

Define internal fun getBrand(): String that returns brand.

3

Add a protected function to get the engine number

Inside the Car class, add a protected function called getEngineNumber that returns the engineNumber variable.

Kotlin

class Car {
    val brand: String = "Toyota"
    private val engineNumber: String = "ENG12345"

    internal fun getBrand(): String {
        return brand
    }

    // Your code here
}

Need a hint?

Define protected fun getEngineNumber(): String that returns engineNumber.

4

Create SportsCar subclass and print accessible members

Create a subclass called SportsCar that inherits from Car. Inside it, create a function showDetails that prints the brand and calls the protected function getEngineNumber(). Then, in the main function, create a SportsCar object and print the result of calling getBrand() and showDetails().

Kotlin

class Car {
    val brand: String = "Toyota"
    private val engineNumber: String = "ENG12345"

    internal fun getBrand(): String {
        return brand
    }

    protected fun getEngineNumber(): String {
        return engineNumber
    }
}

// Your code here

Need a hint?

Create SportsCar subclass with showDetails() printing brand and getEngineNumber(). Then print getBrand() and call showDetails() in main().