Default Imports in Kotlin

Introduction

Default Imports 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.

Kotlin automatically imports commonly used packages. 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

• Kotlin automatically imports commonly used packages.
• kotlin., kotlin.collections. and kotlin.ranges.* are imported by default.
• java.lang.* is also available on JVM platform.

Syntax

// println is available without import

Default Imports in Kotlin Example Program in Kotlin

fun main(args: Array<String>) {
    println("Default imports make println available")
    val list = listOf(1, 2, 3)
    println(list)
}

Sample Output

Default imports make println available
[1, 2, 3]

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. The println("Default imports make println available") statement writes a line to the console — this produces part of the sample output below.

3. val list = listOf(1, 2, 3) assigns or updates a value used later in the program.

4. The println(list) statement writes a line to the console — this produces part of the sample output below.

5. Kotlin automatically imports commonly used packages.

6. 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

• Kotlin automatically imports commonly used packages.
• kotlin., kotlin.collections. and kotlin.ranges.* are imported by default.
• java.lang.* is also available on JVM platform.
• 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.