Manage multiple Java JDK versions on a Mac

As an Android developer, you will most likely have come into contact with Java and its JDK (Java Development Kit). Gradle version 7 and above requires JDK version 11 - which is bundled with Android Studio 2020.3.1 Arctic Fox.

If you have read my post about installing and managing updates of your JDK versions with Android Studio you have found an option to install and update the JDK(s) separate from the Android Studio embedded one. From time to time you may need a specific version for different projects.

Running java from the terminal runs by default the latest installed version. So starting e.g. ./gradlew app:assembleRelease from the terminal will use the Java JDK that is currently set.

Set specific JDK version

Info: /usr/bin/java is not just a symbolic link to a Virtual Machines /bin/java binary. Instead, it behaves like a proxy binary by default - it finds the latest installed JDK and uses that when executing. However, you can instruct it to use a specific version.

If you want to run a specific version you have to specify the environment variable $JAVA_HOME pointing to the path of the version you want to use.

You can list all installed Java versions with the following command:

/usr/libexec/java_home -V

Will show you a list like this

Matching Java Virtual Machines (4):
    11.0.12.1 (x86_64) "Amazon.com Inc." - "Amazon Corretto 11" /Users/joachim/Library/Java/JavaVirtualMachines/corretto-11.0.12/Contents/Home
    1.8.0_312 (x86_64) "Amazon" - "Amazon Corretto 8" /Users/joachim/Library/Java/JavaVirtualMachines/corretto-1.8.0_312/Contents/Home
    1.8.0_302 (x86_64) "Amazon" - "Amazon Corretto 8" /Users/joachim/Library/Java/JavaVirtualMachines/corretto-1.8.0_302/Contents/Home
    1.8.0_275 (x86_64) "Amazon" - "Amazon Corretto 8" /Users/joachim/Library/Java/JavaVirtualMachines/corretto-1.8.0_275/Contents/Home
/Users/joachim/Library/Java/JavaVirtualMachines/corretto-11.0.12/Contents/Home

The last line shows the path to the latest Java home.

You can get the path to a specific version with the following command:

/usr/libexec/java_home -v1.8

This will get the path to the latest installation of the specified version 1.8

/Users/joachim/Library/Java/JavaVirtualMachines/corretto-1.8.0_312/Contents/Home

Combining this you can modify your .zshrc (resp. .bashrc) to set your $JAVA_HOME to a specific version

# Path to JAVA
export JAVA_HOME=$(/usr/libexec/java_home -v1.8)

Starting a terminal now you will see the output of echo $JAVA_HOME resulting in the path

/Users/joachim/Library/Java/JavaVirtualMachines/corretto-1.8.0_312/Contents/Home

And running java -version will show you the version details like this

openjdk version "1.8.0_312"
OpenJDK Runtime Environment Corretto-8.312.07.1 (build 1.8.0_312-b07)
OpenJDK 64-Bit Server VM Corretto-8.312.07.1 (build 25.312-b07, mixed mode)

Change JDK version (temporarily)

You might like to change the version just for your current terminal session a little more convenient with the following function added to your .zshrc

jdk() {
      version=$1
      unset JAVA_HOME;
      export JAVA_HOME=$(/usr/libexec/java_home -v"$version");
      java -version
}

In a new terminal session you will be able to use that function like this

jdk 11

This sets $JAVA_HOME to the latest 11 version path and so java -version will result in

openjdk version "11.0.12" 2021-07-20 LTS
OpenJDK Runtime Environment Corretto-11.0.12.7.2 (build 11.0.12+7-LTS)
OpenJDK 64-Bit Server VM Corretto-11.0.12.7.2 (build 11.0.12+7-LTS, mixed mode)

Setting the version with the fuction jdk will change the version for this session - closing this terminal session and starting a new one will take the value of the $JAVA_HOME set with first export.