Kotlin for Java Developers

There is Coursera's Kotlin for Java Developers which is offered by JetBrains

I was in a similar situation and went through this course to learn kotlin before I started the Google codelabs: https://www.coursera.org/learn/kotlin-for-java-developers

It's from jetbrains directly. When I did the codelabs, I was quite glad that I learned kotlin beforehand, otherwise I probably would have been a bit overwhelmed. I didn't have any prior Android knowledge though

I bailed out of that course: too basic, contrived examples, uninteresting exercises.

Instead I enrolled into and completed Coursera's Kotlin for Java Developers. I liked it better, even if I felt that I was able to understand some lessons only because of my previous exposure to the language.

https://www.coursera.org/learn/kotlin-for-java-developers

I highly recommend Kotlin for Java Developers

Try official jetbrains course on coursera (you don't need to pay if you don't need cert) https://www.coursera.org/learn/kotlin-for-java-developers

Have you done any Java?

If so this is really good:

https://www.coursera.org/learn/kotlin-for-java-developers

There is Kotlin for Java Developers from JetBrains. In contrast to books, it's free.

One of the options is to check the Coursera “Kotlin for Java developers” course (https://www.coursera.org/learn/kotlin-for-java-developers), specifically the part about functional programming. You can do tasks for practice and then watch the video solutions checking whether you used the most idiomatic way to solve the problem.

This Coursera course was made specially for java developers by Kotlin team.

It's concise and practical. No payments required.

https://www.coursera.org/learn/kotlin-for-java-developers

here's the official course from jetbrains on coursera: https://www.coursera.org/learn/kotlin-for-java-developers

All free (and made/supported by JetBrains):

https://play.kotlinlang.org/koans/overview

https://hyperskill.org/

https://www.coursera.org/learn/kotlin-for-java-developers

I highly recommend you to do the Koans because they're simple and teaches you the basics with great examples.

Another thing that the others forgot to mention : I know you want to make an app as quickly as possible, but I'd advise not to forget that learning the basics is REALLY important to make something great (How could you build a building if the first floor ain't stable, y'know).

So I really recommend you to go through those courses above (and not Android courses immediately) to get a grasp on the concepts of Object Oriented and Functional Programming.

Also, don't forget that the documentation will always be your best friend.
https://kotlinlang.org/docs

When you think you got everything up (and did some small console apps/games), you can then start doing mobile apps.

Of course, in the end, the choice is yours, and all I said are just advises, you do you.

Go for Kotlin absolutely. It way better in every way. It takes some time to adjust and have the right reflexes because you have to take the habit to use what's provided instead of writing boilerplate code like we used to in Java.

A great course that helped me a lot is Coursera's Kotlin for Java Developers. Even if you're more used to C#. What's great in this course compared to most of the stuff I've found is that it's for someone who already knows how to code in OO languages. They won't teach you the basics of a class, an object, variables, types, ...