also Operator for Null Handling in Kotlin

Introduction

also Operator for Null Handling is a fundamental concept every Kotlin developer should understand. Null safety is one of Kotlin’s signature features. It catches null-related bugs at compile time instead of crashing at runtime with a NullPointerException.

Also performs an action on an object and returns the object itself. 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

• also performs an action on an object and returns the object itself.
• It is useful for additional actions such as logging while keeping the original reference.
• It can be combined with nullable types for side effects.

Syntax

obj.also { println(it) }

also Operator for Null Handling in Kotlin Example Program in Kotlin

fun main(args: Array<String>) {
    var data: String? = "Sample Data"
    data = data?.also { value ->
        println("Processing: $value")
    }
    println("Final value: $data")
}

Sample Output

Processing: Sample Data
Final value: Sample Data

When to use

Use nullable types when a value may legitimately be absent — optional fields, parsed input, or database lookups that can miss.

How it works

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

2. var data: String? = "Sample Data" assigns or updates a value used later in the program.

3. data = data?.also { value -> assigns or updates a value used later in the program.

4. The println("Processing: $value") statement writes a line to the console — this produces part of the sample output below.

5. The println("Final value: $data") statement writes a line to the console — this produces part of the sample output below.

6. Also performs an action on an object and returns the object itself.

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

• Prefer non-nullable types by default; add ? only when null is a valid state.
• Use safe call (?.) and Elvis (?:) instead of force unwrap (!!) unless you are certain.
• Handle nullable collections and nested properties with ?. chains or let blocks.

Common Mistakes

• Using !! everywhere instead of handling null safely — this reintroduces NPE risk.
• Forgetting that platform types from Java are implicitly nullable.
• Comparing nullable strings with == without considering both sides may be null.

Key Points

• also performs an action on an object and returns the object itself.
• It is useful for additional actions such as logging while keeping the original reference.
• It can be combined with nullable types for side effects.
• 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.