Installation

Source: https://mkyong.com/java/how-to-install-java-on-mac-osx/

Installing OpenJDK on macOS

Install Homebrew.

Run brew search java to find all Java related formulas, e.g.:

==> Formulae
app-engine-java               java11                        jslint4java
google-java-format            javacc                        libreadline-java
java                          javarepl                      pdftk-java
==> Casks
eclipse-java                                 oracle-jdk-javadoc
eclipse-javascript                           homebrew/cask-versions/java-beta

Check the java formula via brew info java, e.g.:

openjdk: stable 16.0.1 (bottled) [keg-only]
Development kit for the Java programming language
https://openjdk.java.net/
Not installed
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/openjdk.rb
License: GPL-2.0-only with Classpath-exception-2.0
==> Dependencies
Build: autoconf ✔
==> Caveats
For the system Java wrappers to find this JDK, symlink it with
  sudo ln -sfn /usr/local/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk

openjdk is keg-only, which means it was not symlinked into /usr/local,
because macOS provides similar software and installing this software in
parallel can cause all kinds of trouble.

Install the latest OpenJDK by running brew install java.

Note

Homebrew does install OpenJDK as a keg, which means the default Java installation at /usr/bin/java is not overwritten, but installed into /usr/local/Cellar/. As mentioned in the brew info java output, it is not recommended to do overwrite the default Java, as it might create lots of issues.

Add installation to /Library/Java/JavaVirtualMachines/ create a symbolic link:

$ sudo ln -sfn /usr/local/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk

Check, if the correct installation is now referenced by running java --version, e.g.:

openjdk 16.0.1 2021-04-20
OpenJDK Runtime Environment Homebrew (build 16.0.1+0)
OpenJDK 64-Bit Server VM Homebrew (build 16.0.1+0, mixed mode, sharing)

Switch between installed Java versions

When installing Java over Homebrew, you should have at least two Java versions installed on your system. All versions can printed out by running /usr/libexec/java_home -V, e.g.:

Matching Java Virtual Machines (2):
    16.0.1 (x86_64) "Homebrew" - "OpenJDK 16.0.1" /usr/local/Cellar/openjdk/16.0.1/libexec/openjdk.jdk/Contents/Home
    14.0.1 (x86_64) "Oracle Corporation" - "Java SE 14.0.1" /Library/Java/JavaVirtualMachines/jdk-14.0.1.jdk/Contents/Home
/usr/local/Cellar/openjdk/16.0.1/libexec/openjdk.jdk/Contents/Home

They are also located in /Library/Java/JavaVirtualMachines and can be called like this:

$ ls -ls /Library/Java/JavaVirtualMachines

0 drwxr-xr-x  3 root  wheel  96 Jun  1  2020 jdk-14.0.1.jdk
0 lrwxr-xr-x  1 root  wheel  42 Aug  9 09:24 openjdk.jdk -> /usr/local/opt/openjdk/libexec/openjdk.jdk

To enable a simple switch, add this content to your ~/.zshrc file (create it, if it does not yet exist):

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

Save and close the file and source it to become active:

$ source ~/.zhsrc

Now you are able to switch to any installed version by running java <version> e.g.:

$ jdk 14

java version "14.0.1" 2020-04-14
Java(TM) SE Runtime Environment (build 14.0.1+7)
Java HotSpot(TM) 64-Bit Server VM (build 14.0.1+7, mixed mode, sharing)

$ jdk 16

openjdk version "16.0.1" 2021-04-20
OpenJDK Runtime Environment Homebrew (build 16.0.1+0)
OpenJDK 64-Bit Server VM Homebrew (build 16.0.1+0, mixed mode, sharing)