Quick guide to download and install OpenJDK 12 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 12 tar distribution openjdk-12.0.2_osx-x64_bin.tar.gz. Here is the quick link to download the OpenJDK 12 tar file openjdk-12.0.2_osx-x64_bin.tar.gz
To Install OpenJDK 12 Java Runtime - Untar the downloaded OpenJKD 9 tar file to a convenient directory say "Downloads".
$ cd ~/Downloads
$ tar xf openjdk-12.0.2_osx-x64_bin.tar.gz
Once the above steps are successfully completed , move the unziped directory to /Library/Java/JavaVirtualMachines/
sudo mv jdk-12.jdk /Library/Java/JavaVirtualMachines/
Once the OpenJDK 12 Download and installation is complete, we can verify the installed OpenJDK 12 version using below Command.
Go to Mac prompt and type java -version
The above command prints the OpenJDK 12 version you installed.
openjdk version "12" xxxx-xx-xx
OpenJDK Runtime Environment xx.x (build 12+xx)
OpenJDK 64-Bit Server VM (build 12+xx, mixed mode)
Note: Here is the list of OpenJDK known-issues OpenJDK Known Issues