Access Modifiers Overview in Kotlin

Introduction

Access Modifiers Overview is a fundamental concept every Kotlin developer should understand. Packages group related classes and functions into namespaces, keep large codebases organized, and control visibility with import statements.

Public is the default visibility in Kotlin. In this tutorial you will learn the syntax, walk through a complete example program, study the sample output, and review best practices so you can apply the concept confidently in your own projects.

Definition

• public is the default visibility in Kotlin.
• private restricts visibility to the same file or class.
• protected and internal are used in class inheritance and modules.

Syntax

private fun helper() { }

Access Modifiers Overview in Kotlin Example Program in Kotlin

class Account {
    private var balance = 100
    fun showBalance() = balance
}

fun main(args: Array<String>) {
    val account = Account()
    println("Balance: ${account.showBalance()}")
}

Sample Output

Balance: 100

When to use

Use packages to separate features (networking, UI, data) and avoid name clashes between similarly named classes.

How it works

1. The program starts with a main function — the entry point that runs when you execute the file.

2. private var balance = 100 assigns or updates a value used later in the program.

3. fun showBalance() = balance assigns or updates a value used later in the program.

4. val account = Account() assigns or updates a value used later in the program.

5. The println("Balance: ${account.showBalance()}") statement writes a line to the console — this produces part of the sample output below.

6. Public is the default visibility in Kotlin.

7. Run the program in IntelliJ IDEA, Android Studio, or with the Kotlin command-line compiler (kotlinc / kotlin). Compare your console output with the sample output shown below.

Best Practices

Common Mistakes

Key Points

• public is the default visibility in Kotlin.
• private restricts visibility to the same file or class.
• protected and internal are used in class inheritance and modules.
• Test the example locally and verify the output matches the sample.
• Experiment by changing input values to see how behaviour changes.

Notes

• Semicolons at the end of statements are optional in Kotlin.