Print Lists Content Separated by Comma

1. Overview

One of the most common operations in software development is to print the content of a List in some specific format.

In this tutorial, we’ll explore different techniques to print a List‘s elements separated by a comma in Kotlin.

2. Using a for Loop

The first technique uses the for control to iterate through the List and manually print the elements separated by commas:

val myList = listOf("apple", "banana", "cherry", "date")
var result = ""
for (item in myList) {
    result += if (result.isEmpty()) item else ", $item"
}
assertEquals("apple, banana, cherry, date", result)

3. Using joinToString Function

Kotlin provides a built-in function joinToString that makes it straightforward to concatenate the elements of a List with a separator:

val myList = listOf("apple", "banana", "cherry", "date")
val result = myList.joinToString(", ")
assertEquals("apple, banana, cherry, date", result)

4. Using the reduce Function

In Kotlin, the reduce method is a higher-order function that is often used for combining the elements of a collection into a single result. We can take advantage of the reduce function to concatenate the elements in the List:

val myList = listOf("apple", "banana", "cherry", "date")
val result = myList.reduce { acc, s -> "$acc, $s" }
assertEquals("apple, banana, cherry, date", result)

5. Conclusion

Printing the contents of a List separated by commas in Kotlin can be achieved using various methods. The joinToString function provides a very concise and readable solution. However, using a for loop or the reduce function can be helpful in situations where we need more manual control over the process.