Java is a language/platform maintained by Oracle. It’s known for it’s “Write-Once-Run-Anywhere” mantra and, in my opinion, for its verbosity.
Kotlin is a cross-platform, statically-typed language that often targets the JVM. It’s used for web development, Android development, and much more.
Android is a mobile operating system designed primarily for touchscreen mobile devices such as smartphones and tablets. Development is done predominantly in Kotlin or Java.
Scala combines object-oriented and functional programming in one concise, high-level language. Note: Most of these examples will be using Scala 2.X