The Java Virtual Machine is a mature and very versatile platform for running software that takes full advantage of modern hardware features. While it is true that Java-based applications once could be considered slow, bloated, and extremely memory-hungry, things have improved greatly over the years. It's no coincidence that many mainstream cloud-based services and websites, which often have to serve tens of thousands users simultaneously, are powered by a JVM-based backend.

While Java is, without a doubt, the most popular language used to create applications that run on the JVM, other languages are getting more and more popular every year. This book covers five different JVM-based languages: Java, Scala, Clojure, Kotlin, and Groovy. Some of those languages are statically typed while others are dynamically typed. Likewise, this book covers both object-oriented programming languages and functional programming languages. The JVM is versatile enough to make this all possible.

By covering all these languages in a single book, you can easily compare each language with the others and, hopefully, pick your favorite language by building the sample projects.