As you can see from the processes involved in this recipe, there is great similarity between Kotlin and Java-based styles of writing Spring 5 applications using Spring Boot 2.0. The only reason for this is that Kotlin provides strong interoperability behavior with libraries compiled in Java 1.8, unlike Groovy.

Groovy is a dynamically-typed and object-oriented language which is considered a popular JVM-based language. Its codes are compiled using static Java compilers to generate bytecodes faster than Java compilation. Its edge is some string and numerical operations which are heavy if executed multiple times in Java. But Groovy fails to execute a majority of Java APIs, unlike Kotlin, which can import almost all of them. Kotlin is also a JVM-based language, but written as an improvement to Java and not to Groovy and other JVM-based languages.

The strength of Kotlin over Java is the clarity and simplicity of its coding convention, which allows developers to focus on the high-level specification of the project. Everything that we have done, from Chapter 2, Learning Dependency Injection (DI) up to this chapter, can be done by Kotlin with less code. Currently, Kotlin can be used to implement Android-based applications because of its shorter and lighter bytecodes. You can learn more about Kotlin through the documentation at https://kotlinlang.org/docs/tutorials/.