Quick guide to download and install OpenJDK 9 on Mac. - OpenJDK Community Version
OpenJDK is the short form of Open Java Development Kit similar to Oracle's Java Development Kit used to develop Java Applications. Main difference between Oracle JDK and OpenJDK is that OpenJDK is free for all while Oracle Java Development Kit or Oracle JDK requires commercial license. For more details refer openjdk vs oracle jdk
If you want to know more about OpenJDK, you can go through Open Java Development Kit Quick guide.
Go to https://jdk.java.net/archive/ and download the OpenJDK 9 tar distribution openjdk-9.0.4_osx-x64_bin.tar.gz. Here is the quick link to download the OpenJDK 9 tar file openjdk-9.0.4_osx-x64_bin.tar.gz
To Install OpenJDK 9 Java Runtime - Untar the downloaded OpenJKD 9 tar file to a convenient directory say "Downloads".
$ cd ~/Downloads
$ tar xf openjdk-9.0.4_osx-x64_bin.tar.gz
Once the above steps are successfully completed , move the unziped directory to /Library/Java/JavaVirtualMachines/
sudo mv jdk-9.jdk /Library/Java/JavaVirtualMachines/
Once the OpenJDK 9 Download and installation is complete, we can verify the installed OpenJDK 9 version using below Command.
Go to Mac prompt and type java -version
The above command prints the OpenJDK 9 version you installed.
openjdk version "9" xxxx-xx-xx
OpenJDK Runtime Environment xx.x (build x+xx)
OpenJDK 64-Bit Server VM (build x+xx, mixed mode)