In the previous chapter, we explored how to migrate pre-Java 9 applications to the new Java platform. We examined several issues that might cause your current applications to have problems when running on Java 9. We started with a review of Project Jigsaw and then looked at how modules fit into the new Java platform. We provided you with insights and processes to get your Java 8 code working with Java 9, 10, or 11. Specifically, we provided tips for migration planning, shared advice from Oracle regarding migration, and shared tools that you can use to help you as you get started with Java 18.x.

In this chapter, we will take our first look at the new command line, the Read-Eval-Print Loop (also referred to as REPL) tool in Java, and the Java Shell (JShell). We will start by going over some introductory information regarding the tool, the REPL concept, and move into the commands and command-line options that you can use with JShell. We will take a practitioner's approach to our review of the JShell and include examples that you can try on your own.

The following topics will be covered in this chapter:

• What is JShell?
• Getting started with JShell
• Practical uses of JShell
• Working with scripts