Safe Call Operator (?.) in Kotlin

Definition

• This operator helps in writing a program without NPEs (Null Pointer Exceptions) and is represented by (?.)
• This operator eliminates exception and returns the response as null when a null value is used for any operation.

Syntax

//When the nullable_value is null, the block inside the let will not be executed.
var result = nullable_value?.let{
	//Block of code
}

For example,

//While doing operations or iterating with a collection which may have null values, this operator can be used to eliminate Null Pointer Exception.
var result = value_in_collection?.let{
	//"it" is a variable generated by Kotlin and it holds the particular non-null value of the collection.
	println(it)
}

Safe Call Operator Example Program in Kotlin

//Safe Call Operator Example Program in Kotlin
//Operator Kotlin Programs, Basic Kotlin Program
fun main(args: Array<String>) {

    //List containing null values
    val namesList = listOf("Sheela", null, "Leela")
    println("List containing null values is : $namesList")

    //Iterating the list
    println("\nIterating the non-null values in list")
    for (value in namesList) {
        //Safe Call Operator allows only the non-null values inside the let block
        value?.let {
            //Printing the non-null value
            println(it)
        }
    }
}

Sample Output

List containing null values is : [Sheela, null, Leela]

Iterating the non-null values in list
Sheela
Leela

How It Works

This Kotlin program demonstrates Safe Call Operator (?.). It first prepares the data it needs, then walks through the data with a loop to compute the result, and finally prints the output shown in the Sample Output above.

1. Declare the variables that hold the program’s data.
2. Iterate over the data using a loop to apply the logic.
3. Print the final result to the console so you can compare it with the sample output.

Try changing the input values and re-running the program to see how the output changes — this is the fastest way to understand how the logic behaves.