Book Image

Introduction to JVM Languages

Book Image

Introduction to JVM Languages

Overview of this book

Anyone who knows software development knows about the Java Virtual Machine. The Java Virtual Machine is responsible for interpreting Java byte code and translating it into actions. In the beginning, Java was the only programming language used for the JVM. But increasing complexity of the language and the remarkable performance of the JVM created an opening for a new generation of programming languages. If you want to build a strong foundation with the Java Virtual Machine and get started with popular modern programming languages, then this book is for you. The book will begin with a general introduction of the JVM and its features, which are common to the JVM languages, helping you get abreast with its concepts. It will then dive into explaining languages such as Java, Scala, Clojure, Kotlin, and Groovy and will show how to work with each language, their features, use cases, and pros and cons. By writing example projects in those languages and focusing on each language’s strong points, it will help you find the programming language that is most appropriate for your particular needs. By the end of the book, you will have written multiple programs that run on the Java Virtual Machine and know about the differences between the various languages.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Procedural programming in Kotlin


While Kotlin is a pure OOP language, it also supports procedural programming. This means that functions and variables can be defined without placing them explicitly in classes, unlike Java and compiled Scala code. (As we have seen earlier, Scala does not require functions and variables to be placed in classes when using its REPL; it requires this when using the standalone scalac compiler.)

When not using Kotlin's REPL interactive shell to write programs, you'll make use of the Kotlin compiler. When you use the compiler to compile your source code, you can place both the functions and properties at the top level of a source file. We have been doing this for a while now in this chapter:

    fun function1 {
      println("function1 is running...")
    }
    var property1: String = "default value of property1"

It's not possible to place executable code at the top level in the source code, though. Executable code must always reside in a function. To create a JVM...