Ben Basten > Posts

Switching Between Java Versions

February 16, 2022

· 5min read

Problem: How do I quickly change between Java versions in the terminal?

I’m currently doing development on an array of different Java apps. For the longest time, all of the apps I was working with only used Java 8. My team is now moving towards a Java 11 stack, so I can’t run these apps with just the Java 8 JDK anymore.

This solution is for the zsh shell on a Mac computer.

The key lies with the JAVA_HOME environment variable. This dictates what version of Java to run when a command is executed. Using aliases, you will be able to quickly set this environment variable.

List out all installed JDKs

Macs have an executable under /usr/libexec/java_home that can quickly list all installed JDKs, and get the Java path for any of these individual JDKs.

Enter the command /usr/libexec/java_home -V to get the list of installed JDKs. The output will look like this:

Matching Java Virtual Machines (2):
    11.0.14 (x86_64) "Oracle Corporation" - "Java SE 11.0.14" /Library/Java/JavaVirtualMachines/jdk-11.0.14.jdk/Contents/Home
    1.8.0_281 (x86_64) "Oracle Corporation" - "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_281.jdk/Contents/Home

There’s 2 installations of Java - 11.0.14 and 1.8.0_281.

Get the path of a specific JDK installation

/usr/libexec/java_home -v 11 will display the path of your Java 11 installation:

/Library/Java/JavaVirtualMachines/jdk-11.0.14.jdk/Contents/Home

If you have even more than 2 installations, you can get the path of a specific Java minor version. For example, /usr/libexec/java_home -v 1.8.0_281 will look like this:

/Library/Java/JavaVirtualMachines/jdk1.8.0_281.jdk/Contents/Home

Changing the Java version

Using these commands to get a Java installation path, you can quickly change the JAVA_HOME environment variable using the export command.

Adding aliases to quickly change versions

  1. cd - navigate to your home directory
  2. With your preferred text editor (nano, vi, vim, etc.), open up the .zshrc file.
    • For example: nano .zshrc
  3. Add the following lines to create new aliases:
    alias home='echo $JAVA_HOME'
alias java8='export JAVA_HOME=`/usr/libexec/java_home -v 1.8.0_281`'
alias java11='export JAVA_HOME=`/usr/libexec/java_home -v 11`'
  4. Save, and restart the terminal for the changes to be applied.

Now, to change the Java versions the following commands can be used:

Happy coding!