Java is an immensely popular programming language, and managing multiple Java versions can be a challenging task. That’s where jEnv comes in handy. In this blog post, we’ll cover jEnv’s most used features, including installation instructions for various platforms, and help you manage your Java versions with ease.

I. Overview

jEnv is a command-line tool that enables you to manage multiple Java versions on your system. It allows you to set your desired Java version per project, shell session, or system-wide. By using jEnv, you can avoid conflicts between different projects that require different Java versions and ensure a smoother development experience.

II. Installation

Mac

To install jEnv on macOS, you can use the Homebrew package manager. If you haven’t installed Homebrew yet, you can find the installation instructions here.

brew install jenv

After installation, add the following lines to your ~/.bash_profile, ~/.zshrc, or ~/.bashrc file, depending on your shell:

export PATH="$HOME/.jenv/bin:$PATH"
eval "$(jenv init -)"

Linux

To install jEnv on Linux, execute the following commands:

git clone https://github.com/jenv/jenv.git ~/.jenv

After cloning the repository, add the following lines to your ~/.bashrc or ~/.zshrc file, depending on your shell:

export PATH="$HOME/.jenv/bin:$PATH"
eval "$(jenv init -)"

III. Usage

local

The local command sets the Java version for a specific directory. This is useful when working on multiple projects with different Java version requirements.

jenv local 11.0.2

global

The global command sets the default Java version for the entire system. This version will be used if no other version is specified by the local or shell commands.

jenv global 11.0.2

shell

The shell command sets the Java version for the current shell session. This is useful when you want to temporarily use a different Java version without affecting other projects or sessions.

jenv shell 11.0.2

rehash

The rehash command generates shims for all Java executables known to jEnv. This is useful after installing new Java versions or when jEnv doesn’t recognize some Java executables.

jenv rehash

version

The version command displays the currently active Java version.

jenv version

versions

The versions command lists all installed Java versions and marks the currently active version with an asterisk.

jenv versions

which

The which command shows the path to the Java executable of the currently active version.

jenv which java

whence

The whence command lists all the Java versions that contain a specific command.

jenv whence java

add

The add command registers a new Java version with jEnv. You need to provide the path to the Java installation directory.

jenv add /path/to/java/home

IV. Conclusion

jEnv is a powerful tool that simplifies Java version management. With features like local, global, and shell, you can easily switch between Java versions on a per-project or per-session basis. The rehash, version, versions, which, whence, and add commands further enhance your ability to manage and organize your Java installations. By using jEnv, you can streamline your development workflow, avoid version conflicts, and ensure that your projects run on the desired Java version. Whether you’re working on multiple Java projects or simply want to have greater control over your Java environment, jEnv is an indispensable tool for Java developers.