What Is jEnv?

jEnv is a JDK version manager. It lets you install multiple JDKs and switch between them easily. This post covers installation and usage on macOS.


Install and Configure jEnv

On macOS, install with Homebrew:

$ brew install jenv

After installation, check the configured JDKs. If you have not added any versions yet, the list is empty.

$ jenv versions
 * system (set by /Users/madplay/.jenv/version)

To list all installed JDKs, run /usr/libexec/java_home -V, or browse /Library/Java/JavaVirtualMachines.

$ /usr/libexec/java_home -V
Matching Java Virtual Machines (3):
  11.0.2, x86_64:  "OpenJDK 11.0.2"	/Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home
  1.8.0_73, x86_64: "Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_73.jdk/Contents/Home
  1.7.0_79, x86_64:	"Java SE 7"	/Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home

If no JDK is installed, you can use a cask package (latest version):

$ brew cask install java

Now initialize jEnv.

$ echo 'export PATH="HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(jenv init -)"' >> ~/.bash_profile

If settings do not apply, edit .bash_profile directly:

$ sudo vi ~/.bash_profile
if which jenv > /dev/null; then eval "$(jenv init -)"; fi

Reload your shell:

$ source ~/.bash_profile


Use jEnv

Add installed JDK versions with jenv add.

In a fresh environment, ~/.jenv/versions may not exist. Create it first.

# create jenv version directory
# -p creates intermediate directories
$ mkdir -p ~/.jenv/versions

# add JDK 1.7
$ jenv add /Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home/
oracle64-1.7.0.79 added
1.7.0.79 added
1.7 added

# add JDK 1.8
$ jenv add /Library/Java/JavaVirtualMachines/jdk1.8.0_73.jdk/Contents/Home/
oracle64-1.8.0.73 added
1.8.0.73 added
1.8 added

# add JDK 11
$ jenv add /Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home/
openjdk64-11.0.2 added
11.0.2 added
11.0 added

Verify:

$ jenv versions
* system (set by /Users/madplay/.jenv/version)
  1.7
  1.7.0.79
  1.8
  1.8.0.73
  11.0
  11.0.2
  openjdk64-11.0.2
  oracle64-1.7.0.79
  oracle64-1.8.0.73

Set a global version:

$ jenv global 11.0.2
$ java -version
openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)

Set a local version for the current directory:

$ jenv local 1.8

$ java -version
java version "1.8.0_73"
Java(TM) SE Runtime Environment (build 1.8.0_73-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.73-b02, mixed mode)


A Deeper Look

When you set a local version, jEnv writes a .java-version file containing the version string.

After running jenv add, jEnv creates symbolic links under ~/.jenv/versions that point to the real JDK directories.

$ pwd
/Users/madplay/.jenv/versions
$ ls -al
lrwxr-xr-x   1 madplay  madplay   63  3  25 23:03 1.7 -> /Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home
lrwxr-xr-x   1 madplay  madplay   63  3  25 23:06 1.8 -> /Library/Java/JavaVirtualMachines/jdk1.8.0_73.jdk/Contents/Home
lrwxr-xr-x   1 madplay  madplay   66  3  25 23:06 11.0 -> /Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home
lrwxr-xr-x   1 madplay  madplay   66  3  25 23:06 openjdk64-11.0.2 -> /Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home
lrwxr-xr-x   1 madplay  madplay   63  3  25 23:03 oracle64-1.7.0.79 -> /Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home
lrwxr-xr-x   1 madplay  madplay   63  3  25 23:06 oracle64-1.8.0.73 -> /Library/Java/JavaVirtualMachines/jdk1.8.0_73.jdk/Contents/Home
# ... omitted

which java also points to jEnv shims:

$ which java
/Users/madplay/.jenv/shims/java

# without jEnv
$ which java
/usr/bin/java

To uninstall, remove both the package and its directory. If you only uninstall, you may see: /usr/local/Cellar/jenv/0.5.2/libexec/libexec/jenv: No such file or directory.

$ brew uninstall jenv
$ rm -rf ~/.jenv


Closing Thoughts

jEnv makes Java version switching faster than editing environment variables.

I looked for an IntelliJ plugin but did not find one. There are IntelliJ plugin APIs with many features, so a custom plugin may be possible.

Update: I built and released a plugin so IntelliJ can use jEnv. Building it at night is not easy, but it is done. For details, see the post below.