Mac OS X and multiple Java versions

The cleanest way to manage multiple java versions on Mac is to use Homebrew.

And within Homebrew, use:

homebrew-cask to install the versions of java
jenv to manage the installed versions of java

As seen on http://hanxue-it.blogspot.ch/2014/05/installing-java-8-managing-multiple.html , these are the steps to follow.

install homebrew
install homebrew jenv
install homebrew-cask
install a specific java version using cask (see "homebrew-cask versions" paragraph below)
add this version for jenv to manage it
check the version is correctly managed by jenv
repeat steps 4 to 6 for each version of java you need

homebrew-cask versions

Add the homebrew/cask-versions tap to homebrew using:

brew tap homebrew/cask-versions

Then you can look at all the versions available:

brew search java

Then you can install the version(s) you like:

brew cask install java7
brew cask install java6

And add them to be managed by jenv as usual.

jenv add <javaVersionPathHere>

I think this is the cleanest & simplest way to go about it.

Another important thing to note, as mentioned in Mac OS X 10.6.7 Java Path Current JDK confusing :

For different types of JDKs or installations, you will have different paths

You can check the paths of the versions installed using /usr/libexec/java_home -V, see How do I check if the Java JDK is installed on Mac?

On Mac OS X Mavericks, I found as following:

1) Built-in JRE default: /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home

2) JDKs downloaded from Apple: /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/

3) JDKs downloaded from Oracle: /Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home

Resources

Removing Java 8 JDK from Mac
http://hanxue-it.blogspot.ch/2014/05/installing-java-8-managing-multiple.html
http://sourabhbajaj.com/mac-setup/index.html
http://brew.sh
https://github.com/Homebrew/homebrew/tree/master/share/doc/homebrew#readme
http://sourabhbajaj.com/mac-setup/Homebrew/README.html
"brew tap” explained https://github.com/Homebrew/homebrew/blob/master/share/doc/homebrew/brew-tap.md
“brew versions” explained Homebrew install specific version of formula? and also https://github.com/Homebrew/homebrew-versions
https://github.com/caskroom/homebrew-cask
“cask versions”, similar to “brew versions”, see https://github.com/caskroom/homebrew-versions and also https://github.com/caskroom/homebrew-cask/issues/9447
http://www.jenv.be
https://github.com/gcuisinier/jenv

For macOS Sierra 420

This guide was cobbled together from various sources (replies above as well as other posts), and works perfect.

0. If you haven't already, install homebrew.

See https://brew.sh/

1. Install jenv

brew install jenv

2. Add jenv to the bash profile

if which jenv > /dev/null; then eval "$(jenv init -)"; fi

3. Add jenv to your path

export PATH="$HOME/.jenv/shims:$PATH"

4. Tap "homebrew/cask-versions"

FYI: "Tap" extends brew's list of available repos it can install, above and beyond brew's default list of available repos.

brew tap homebrew/cask-versions

5. Install the latest version of java

brew install java --cask

6. Install java 6 (or 7 or 8 whatever you need)

brew install java6 --cask
#brew install java7 --cask
#brew install java8 --cask

? Maybe close and restart Terminal so it sees any new ENV vars that got setup.

7. Review Installations

All Java version get installed here: /Library/Java/JavaVirtualMachines lets take a look.

ls -la /Library/Java/JavaVirtualMachines

8. Add each path to jenv one-at-a-time.

We need to add "/Contents/Home" to the version folder. WARNING: Use the actual paths on your machine... these are just EXAMPLE's

jenv add /Library/Java/JavaVirtualMachines/1.6.0___EXAMPLE___/Contents/Home
jenv add /Library/Java/JavaVirtualMachines/jdk-9.0.1.jdk___EXAMPLE___/Contents/Home

9. Check if jenv registered OK

jenv versions

10. Set java version to use (globably)

Where XX matches one of the items in the versions list above.

jenv global XX

Check java version

java -version

Check jenv versions

Should also indicate the current version being used with an asterisk.

jenv versions

DONE

Quick future reference

To change java versions

... See the list of available java versions

jenv versions

... then, where XX matches an item in the list above

jenv global XX

Uninstall jdk8, install jdk7, then reinstall jdk8.

My approach to switching between them (in .profile) :

export JAVA_7_HOME=$(/usr/libexec/java_home -v1.7)
export JAVA_8_HOME=$(/usr/libexec/java_home -v1.8)
export JAVA_9_HOME=$(/usr/libexec/java_home -v9)

alias java7='export JAVA_HOME=$JAVA_7_HOME'
alias java8='export JAVA_HOME=$JAVA_8_HOME'
alias java9='export JAVA_HOME=$JAVA_9_HOME'

#default java8
export JAVA_HOME=$JAVA_8_HOME

Then you can simply type java7 or java8 in a terminal to switch versions.

(edit: updated to add Dylans improvement for Java 9)