Java Version Management Manual with jEnv

1. Overview

jEnv is a CLI tool that lets you install multiple Java versions on your system and switch between them by

global, directory (local), and shell session.

On macOS, it automatically recognizes JDKs installed at the /Library/Java/JavaVirtualMachines path.

2. Installation

(1) Install via Homebrew

brew install jenv

(2) Register Environment Variables

After installation, add the following lines to ~/.zshrc (or ~/.bash_profile).

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

Apply:

source ~/.zshrc

3. Checking and Registering Java Versions

(1) Check Installed JDK List on the System

/usr/libexec/java_home -V

Example output:

Matching Java Virtual Machines (3):
    17.0.8 (arm64) "Oracle Corporation" - "Java SE 17"
        /Library/Java/JavaVirtualMachines/jdk-17.0.8.jdk/Contents/Home
    11.0.21 (arm64) "Adoptium" - "OpenJDK 11"
        /Library/Java/JavaVirtualMachines/jdk-11.0.21.jdk/Contents/Home

(2) Register a Version with jEnv

jenv add /Library/Java/JavaVirtualMachines/jdk-17.0.8.jdk/Contents/Home
jenv add /Library/Java/JavaVirtualMachines/jdk-11.0.21.jdk/Contents/Home

Check the registered list:

jenv versions

Example output:

* system (set by /Users/chris/.jenv/version)
  17.0.8
  11.0.21

4. Switching Versions

(1) Global Switch

The version applied by default across all terminals:

jenv global 17.0.8

Verify:

java -version

(2) Local (Directory) Switch

The version applied only within a specific project directory:

cd ~/workspace/myapp
jenv local 11.0.21

A .java-version file will be created in that directory:

11.0.21

(3) Session Switch

Temporarily switch only for the current terminal session:

jenv shell 17.0.8

5. Enabling Plugins

Some build tools (Maven, Gradle, etc.) may not recognize the JAVA_HOME set by jEnv.

In that case, you need to activate the plugin with the command below.

jenv enable-plugin export

After activation, restart the terminal or run:

exec $SHELL -l

jEnv will now automatically manage the JAVA_HOME environment variable.

6. Checking Environment Variables

echo $JAVA_HOME

Expected output:

/Users/chris/.jenv/versions/17.0.8

7. jEnv Command Summary

Command	Description
`jenv add <경로>`	Register a new JDK with jEnv
`jenv versions`	Check the list of registered versions
`jenv global <버전>`	Set the global default version
`jenv local <버전>`	Set a version for the current directory only
`jenv shell <버전>`	Set a version for the current terminal session only
`jenv enable-plugin export`	Enable automatic JAVA_HOME management
`jenv which java`	Check the currently active Java path
`jenv doctor`	Inspect for configuration issues

8. Per-Project Management Example

Assume you have the following project structure:

~/projects/
├── backend-java11/
│   └── .java-version → 11.0.21
└── backend-java17/
    └── .java-version → 17.0.8

In this case, entering cd backend-java11 will automatically switch to Java 11,

and entering cd backend-java17 will automatically switch to Java 17.

9. Troubleshooting

Issue	Cause	Solution
`java -version` shows system version instead of jEnv version	`export` plugin not activated	Run `jenv enable-plugin export` and restart the shell
`.java-version` is not being applied	Must enter the directory first	Refresh with `cd .` command or `exec $SHELL -l`
`jenv: no such command`	PATH or initialization is missing	Add `eval "$(jenv init -)"` to `.zshrc`
jEnv version not reflected in IDE	IDE not referencing `JAVA_HOME`	Specify the JDK path directly in IDE settings

10. Recommended Workflow

Install multiple JDKs via Homebrew

brew install openjdk@17
brew install openjdk@11

Confirm paths with /usr/libexec/java_home -V
Register each version with jEnv
Activate jenv enable-plugin export
Create a .java-version file per project

With this setup,

you can reliably manage projects that require different JDK versions per build environment.

11. Appendix: JDK Installation Path Examples (macOS)

Version	Path
OpenJDK 17	`/Library/Java/JavaVirtualMachines/openjdk-17.jdk/Contents/Home`
Temurin 11	`/Library/Java/JavaVirtualMachines/temurin-11.jdk/Contents/Home`
Zulu 8	`/Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home`