Scalable Human Blog

Java 9 introduced a tool that revolutionized how Java developers experiment with their code: JShell. This interactive shell, also known as REPL (Read-Eval-Print-Loop), enables Java developers to execute arbitrary Java code snippets without the need for wrapping them in classes or methods. In this post, we’ll explore JShell and how it can enhance your Java development experience.

JShell: The Java REPL

A common practice in Java development involves writing a small piece of code, compiling it, and running it to see the output. This can become tedious, especially when trying out new ideas or learning the language. Enter JShell.

JShell allows developers to execute Java code snippets (expressions, statements, definitions), and see the results instantly. Here’s a simple example:

jshell> System.out.println("Hello, World!") Hello, World!

Key Features of JShell

Here are a few key features that make JShell a potent tool in a Java developer’s arsenal:

1. Tab Completion: Pressing the Tab key will autocomplete your current statement, showing method signatures or variable names.
2. Automatic Semicolon Insertion: JShell is not strict about the need for a semicolon at the end of a statement.
3. Built-In Editor: JShell includes a built-in text editor for multi-line inputs.
4. Forward References: You can reference methods and variables before they are defined.

Benefits of Using JShell

JShell can significantly enhance the developer experience:

• Learning Tool: Beginners can learn Java’s syntax and explore its APIs without the need to create a full-fledged application.
• Rapid Prototyping: Developers can quickly try out code snippets, accelerating the development process.
• Debugging and Testing: JShell is useful for testing small code snippets during development or debugging.

Conclusion

JShell is a powerful tool that brings the interactivity of a REPL to the Java ecosystem. Whether you’re learning Java, testing a tricky piece of code, or quickly prototyping ideas, JShell can streamline the process and enhance your productivity as a Java developer. Embrace the power of interactive Java coding with JShell and elevate your Java development experience.

📚 Further Reading & Related Topics

If you’re exploring JShell, the interactive Java REPL, these related articles will provide deeper insights:

• JShell in IntelliJ, VSCode, and the JShell Terminal – Learn how to use JShell effectively across different environments, including IntelliJ, VSCode, and the JShell terminal, to improve your Java development workflow.

• Mastering Dependency Management with Maven – Discover how to use Maven alongside JShell for managing Java project dependencies and running code interactively for quick testing and debugging.