Using Jenv

Jenv is a command line tool, which you can use to conviniently switch between various version of java. I have used this to check if my Java 8 code base will it work on Java 11.

Basic installation steps are provided [here] https://www.jenv.be/

Checkout the additional configurations here https://github.com/jenv/jenv

At a high level these are the steps to follow to setup for the first time. If you already have it setup jump to switching versions section.

Setup

1. Run git clone https://github.com/gcuisinier/jenv.git ~/.jenv to install jenv

2. Run echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile to add the jenv bin dir to your path.

   • NOTE: In linux echo 'PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
3. Run echo 'eval "$(jenv init -)"' >> ~/.bash_profile to initialize jenv on startup
4. Run mkdir -p ~/.jenv/versions to create jenv’s home dirs (since it doesn’t do it automatically)

5. Run jenv add <path-to-jdk> to add the JDK you installed earlier to jenv.

   • NOTE: See which version is currently being used in the shell java -version
   • To locate the executable which java
   • To find the actual path readlink -f <executable path>
   • NOTE: In mac os jenv add /Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home This might not be the exact path of your JDK.
   • You can use autocomplete to get to the correct dir
   • Just start with /Library/Java/JavaVirtualMachines and start tabbing
   • Make sure your dir ends with Contents/Home if you are on Mac OS
   • NOTE: In linux jenv add /usr/lib/jvm/java-11-openjdk-amd64
   • NOTE: If you recieve an error, use the command source ~/.bash_profile or close the shell and open again.

6. Run jenv global openjdk-11.0.2.jdk to configure your global jdk version

   • NOTE: Might not be the exact version. Check the output of your jenv versions
7. Run jenv enable-plugin export to allow jenv to set your $JAVA_HOME, then create a new terminal session

Adding new version of Java

1. Download the java tarball from https://jdk.java.net/archive
2. Untar the file and move it to desired location.

3. Run jenv add <location>

   • NOTE: In linux, download and extract JDK 14.
   • curl https://download.java.net/java/GA/jdk14/076bab302c7b4508975440c56f6cc26a/36/GPL/openjdk-14_linux-x64_bin.tar.gz | sudo tar -xzvf - --directory /usr/lib/jvm
   • Add to jenv jenv add /usr/lib/jvm/jdk-14

Switching between versions in shell

1. jenv versions
2. jenv shell <desired version>
3. java -version

Other tips

See which version is currently being used in the shell java -version To locate the executable which java To find the actual path readlink -f <executable path> If you are using java set by jenv, to locate executable run jenv which java. Use this path in the readlink command to find jdk installation location.