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 (15 chapters)

Scala's Read-Eval-Print-Loop shell


The scala command demonstrated in the preceding section starts the Scala interactive shell, also known as Scala's Read-Eval-Print-Loop (REPL) environment. You enter a line and the REPL program evaluates it and prints a response (if applicable). It does this in an infinite loop until you quit the program.

In the Scala shell, you can write Scala code interactively. Because Scala is a compiled language, not an interpreted language, you can dynamically enter and execute Scala code in this program. Under the hood, Scala compiles your code and runs the compiled version. The Scala interactive shell is meant for trying Scala expressions, not for writing full programs. It is ideal for trying out the snippets in this chapter. The shell has commands of its own. Enter the :help command and press Enter to see all the shell commands.

In this chapter, we will only use the scala command to run Scala code. In the next chapter, we will cover the scalac compiler. To run code...