Read multiline data from console in Kotlin

This post will discuss how to read multiline data from the console in Kotlin.

1. Using `Scanner`

We can use two scanners, where the first scanner fetches each line with the Scanner.nextLine() function, and the second scanner scan through it using Scanner.next().

import java.util.Scanner

fun main() {

val scanner = Scanner(System.`in`)

while (scanner.hasNextLine()) {

val tokens = mutableListOf<String>()

val lineScanner = Scanner(scanner.nextLine())

while (lineScanner.hasNext()) {

tokens.add(lineScanner.next())

}

lineScanner.close()

println(tokens)

}

scanner.close()

}

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The above solution can be optimized to only use a single scanner. The idea is to read tokens from each line using the split() function from the String class.

import java.util.Scanner

fun main() {

val scanner = Scanner(System.`in`)

while (scanner.hasNextLine()) {

val tokens = scanner.nextLine().split("\\s".toRegex()).toTypedArray()

println(tokens.contentToString())

}

scanner.close()

}

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Here’s equivalent code using only Scanner.next():

import java.util.*

fun main() {

val tokens = mutableListOf<String>()

val scanner = Scanner(System.`in`)

while (scanner.hasNext()) {

tokens.add(scanner.next())

}

scanner.close()

println(tokens)

}

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2. Using `BufferedReader`

Another option to read multiline input from the console in Kotlin is using the BufferedReader class, which is synchronized. The following example demonstrates this by reading each line with the readLine() function and then using the split() function to split it into the individual tokens (using whitespace as a separator).

import java.io.BufferedReader

import java.io.IOException

import java.io.InputStreamReader

fun main() {

val br = BufferedReader(InputStreamReader(System.`in`))

var line: String

try {

while (br.readLine().also { line = it } != null) {

val tokens = line.split("\\s".toRegex()).toTypedArray()

println(tokens.contentToString())

}

br.close()

} catch (e: IOException) {

e.printStackTrace()

}

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To close all resources properly, consider using the use block:

import java.io.BufferedReader

import java.io.InputStreamReader

fun main() {

try {

InputStreamReader(System.`in`).use { inp ->

BufferedReader(inp).use { buffer ->

var line: String

while (buffer.readLine().also { line = it } != null) {

val tokens = line.split("\\s".toRegex()).toTypedArray()

println(tokens.contentToString())

}

} catch (e: Exception) {

e.printStackTrace()

}

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That’s all about reading multiline data from the console in Kotlin.

Read multiline data from console in Kotlin

1. Using Scanner

2. Using BufferedReader

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1. Using `Scanner`

2. Using `BufferedReader`