Mac JDK version control

It may be necessary to run multiple versions of JDK for development or build purposes.

In my case, I was at JDK13. Gradle build was not yet caught up to 13, so I needed up to 11

$ brew update
$ brew tap homebrew/cask-versions

Look at all the versions available:
$brew search java

install the version(s) you like:
$brew cask install java11

$ brew install jenv
$ echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(jenv init -)"' >> ~/.bash_profile
$ source ~/.bash_profile

=========

$ jenv versions
* system (set by /Users/ckendall/.jenv/version)

$ /usr/libexec/java_home -V
 13, x86_64:	"OpenJDK 13"	/Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home
 11.0.2, x86_64:	"OpenJDK 11.0.2"	/Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home

$ jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home
  openjdk64-13 added
  13 added

$ jenv add /Library/Java/JavaVirtualMachines/openjdk-11.0.2.jdk/Contents/Home
  openjdk64-11.0.2 added
 11.0.2 added
 11.0 added

$ jenv versions
* system (set by /Users/ckendall/.jenv/version)
  11.0
  11.0.2
  13
  openjdk64-11.0.2
  openjdk64-13

$ java -version
openjdk version "13" 2019-09-17
OpenJDK Runtime Environment AdoptOpenJDK (build 13+33)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 13+33, mixed mode, sharing)

$ jenv global openjdk64-11.0.2

$ java -version
openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)