I m starting off w Kotlin and I was wondering for retrieving console input is it preferable to use `readLine ` from the <http kotlin io|kotlin io> package or to use `Scanner System `in` ` from the <http java io|java io> package I think my personal preference is going the Java route because I feel that returning `String ` from `readLine ` is something I don t want to deal with But maybe I m not using Kotlin s null safety as much as I should be

From reading the docs, I feel that it's better to use the Java scanner if I'm doing console input since the Kotlin way may be overkill w/ null safety. But since the Kotlin way can return null when reading file input, I think Kotlin's io is better here.

Matteo Mirk

05/25/2021, 8:02 AM

using Java Scanner you have to deal with the hasNext()/next() paradigm and exceptions, with readLine() just with a nullable type: there’s no match in code simplicity when using Kotlin stdlib. I suggest you read a little more about nullable types and don’t be scared by them, it’s a good feature 😉

for example

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readLine()?.let { println("a non null input: $it") }

Jiddles

05/25/2021, 1:20 PM

If Im not wrong, using stdlib makes cross platform easier?

Matteo Mirk

05/26/2021, 8:32 AM

Also that, yes. Not everything inside stdlib is MPP, but you can always check in the docs, they have related badges in the right corner. Anyway, readLine() is compatible with JVM and Native

Justin Yue

05/26/2021, 5:13 PM

Apologies for not answering sooner. I definitely agree readLine() with a nullable type is great. However, my understanding is that it doesn't return null unless it reaches the end of a file when reading a file?

Matteo Mirk

05/28/2021, 7:19 AM

Yes exactly, but only if you attach standard input stream to a file, otherwise it will read from the command line by default here are some examples: https://www.journaldev.com/19757/kotlin-print-println-readline-scanner-repl#using-readline

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