A Simple Guide to Installing Multiple JDK Versions on macOS with jEnv

Configuring the Java home on macOS can be a bit tricky, especially when dealing with multiple JDK versions. Recently, I found a solution that makes the process as simple as it is in Windows. This guide will walk you through the steps to install and manage multiple JDK versions using jEnv, a powerful command-line tool specifically designed for macOS.

Introduction to jEnv

jEnv is a tool that simplifies the management of multiple Java versions on your macOS system. It allows you to easily install, switch between, and manage various versions of the JDK, ensuring that your projects always use the correct version of Java. This guide will help you set up jEnv and get started with managing multiple JDK versions on your macOS development environment.

Prerequisites

The easiest way to install jEnv is through Homebrew, a popular macOS package manager. If you haven't installed Homebrew yet, follow these steps to install it:

Open your terminal. Run the following command to install Homebrew: ruby -e "$(curl -fsSL )"

After installing Homebrew, you can proceed to install jEnv using Homebrew itself.

Installation and Setup

Once Homebrew is installed, you can install jEnv by running the following command:

brew install jenv

After the installation is complete, you need to set up jEnv to work with your macOS system. Add the following lines to your `.zshrc` or `.bashrc` file, depending on your shell:

export PATH"$$PATH" eval "$(jenv init -)"

After adding these lines, restart your terminal or run the following command to apply the changes:

source ~/.zshrc

Now, jEnv is properly set up and ready to use.

Using jEnv to Manage JDK Versions

With jEnv installed and configured, you can start managing multiple JDK versions on your system. Here’s a step-by-step guide to installing and switching between different JDK versions using jEnv:

Installing JDK Versions

To install a specific JDK version, use the following command:

jenv install -b adoptopenjdk-version

For example, to install JDK 8, run:

jenv install -b adoptopenjdk-8

After the installation is complete, you can list all the installed JDK versions using:

jenv versions

Switching between JDK Versions

Use the following command to set a specific JDK version as the current version:

jenv global version

For example, to set JDK 8 as the global version, run:

jenv global 1.8.0_282

To set a local version for a specific project, navigate to the project directory and run:

jenv local version

For example, to set JDK 11 for a project in the current directory, run:

jenv local 11

Virtual Machines and Planning

When managing multiple JDK versions, it’s important to plan your setup carefully. Start with the lowest version and install subsequent versions in numeric order. Only one version will be set as the default, but others can stay installed. You can switch between them as needed.

For example, if you need multiple versions, you can install them in the following order:

1.8.0_282 9-ea 11.0.1

Ensure that the last version you install will be the default, but you can use the others if necessary. Eclipse or any other IDE will automatically detect all installed JDK versions.

Conclusion

Managing multiple JDK versions can be a complex task, but with the help of jEnv, it becomes much simpler. By using jEnv, you can easily install, switch between, and manage various Java versions on your macOS system. This makes it an invaluable tool for Java developers working on different projects with different requirements.