A new report estimates Kotlin will surpass Java as the primary programming language used for Android apps by December 2018. Kotlin was a little-known programming language that was built to run on the Java Virtual Machine, but could also be compiled to JavaScript and could interoperate with Java. Google officially announced earlier this year, at the Google I/O 2017 conference, that Kotlin would become the first third-party supported programming language for apps, besides Java. Among developers, Kotlin is considered Android’s version of Swift, the language Apple introduced for iOS.
Source: https://www.bleepingcomputer.com/news/mobile/kotlin-expected-to-surpass-java-as-android-default-programming-language-for-apps/