You can use Kotlin and Java files in the same project, and they will work nicely together.
https://arctouch.com/2017/05/kotlin-vs-java/
https://kotlinlang.org/
https://medium.com/@octskyward/why-kotlin-is-my-next-programming-language-c25c001e26e3
https://www.guru99.com/kotlin-tutorial.html
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