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Which Java You Got?
Different Javas
Install Jenv to manage multiple Versions of Java
Update Java

Download Java for OS X 2017-001 Java for macOS 2017-001 installs the legacy Java 6 runtime for macOS 10.13 High Sierra, macOS 10.12 Sierra, macOS 10.11 El Capitan, macOS 10.10 Yosemite, macOS 10.9 Mavericks, macOS 10.8 Mountain Lion, and macOS 10.7 Lion. 1.6 Test it, by default, Mac takes the highest version. $ java -version openjdk version '11.0.6' 2020-01-14 OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.6+10) OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.6+10, mixed mode).

There are several ways to install Java.This is a deep dive into the various editions to equip you to debug JVM installation issues.

Which Java You Got?

Open a Terminal session.
Shell scripts check if Java is available by:
Alternately, the older form is:
Either way, the response:
PROTIP: File “java” in the above path is a binary file.
To see what Java VM you have already installed:
PROTIP: -version is a non-standard parameter. Most other programs use either the -v flag or two-dash --version with the longer-form parameter name.
A sample response:
List which versions are installed on your machine:
PROTIP: On Macs, all known JVM’s are located at:
/Library/Java/JavaVirtualMachines/
NOTE: This directory is at the root for the whole machine, not a particular user’s home folder.
The response on my machine:
PROTIP: The Java program looks for the $JAVA_HOME environment variable to obtain files:
echo $JAVA_HOME
Sample response:
PROTIP: This command is my preferred way to see what a machine has becauseif you invoke java or javac, if it’s not installed, MacOS prompts you to install the JDK. Clever. But don’t do it if you want other version of Java.
Java is used by Groovy, Grails, Spring Boot, and others.
PROTIP: Developers use the JDK rather than the JRE (Runtime Environment) in order to get the javac compiler. See what version of the Java Compiler is installed:
A sample response:
Additional details are provided with this command:
That’s a capital -V.
The response on my machine:
Alternately:
Apple Java
PROTIP: The version that comes installed on Apple Macs is obsolete and thus does not have the latest security patches. But do NOT delete the default version.
But if you did uninstall it, to re-install Java 6 for OS X 2014-001,it can be obtained fromhttps://support.apple.com/kb/DL1572?locale=en_US
Different Javas
https://en.wikipedia.org/wiki/List_of_Java_virtual_machines lists all the known Java compilers.Several organizations work on OpenSDK specs from AdoptOpenJDK and certified for Java SE TCK compliance on x64 reference architecture systems
- When Oracle acquired Sun, the jdk (Java Development Kit) was one of the products obtained. Versions are downloaded directly from Oracle from http://jdk.java.net.
- https://adoptopenjdk.net/ has both 8, 11, and 13 running the tradition “HotSpot” JVM and the more recent and faster “OpenJ9” JVM. To install the latest (v13):
- Azul Zuludownloads for macOS, from a company that also sells Java optimization products. Its zulu8.30.0.1-jdk8.0.172-macosx_x64 from zip April 18, 2018 is 179.2 MB expanded
- IBM OpenJDK with Eclipse OpenJ9
Latest Version of Oracle Java
PROTIP: Hold off downloading the java .dmg installer fileas described athttps://java.com/en/download/help/mac_install.xml
WARNING: Oracle installs an annoying Ask Toolbar, without asking.
Oracles docs on installing the JDK:
https://docs.oracle.com/javase/8/docs/technotes/guides/install/mac_jdk.html
Use an internet browser to
http://www.oracle.com/technetwork/java/javase/downloads/index.html
Click the “Download” button for the JDK (not the JRE).
NOTE: Downloads of the JDK contains the JRE.

Install Jenv to manage multiple Versions of Java

PROTIP: If you’re a developer, you’ll likely need to manage different versions of Java needed by different apps. Much like NPM for Node and rbenv for Ruby.

http://hanxue-it.blogspot.com/2014/05/installing-java-8-managing-multiple.html?q=java
describes the steps.

Install Jenv by specifying the location URL: https://raw.githubusercontent.com/entrypass/jenv/homebrew/homebrew/jenv.rb
brew install jenv
The response:
To see if jenv can run, list its version and commands:
jenv
The response is like this (at time of writing Oct 15, 2018):
See where it was installed:
which jenv
My response:
NOTE: The file jenv is a binary executable.
Use Homebrew’s directories rather than ~/.jenv add to the bottom of your bash_profile file:
export JENV_ROOT=/usr/local/var/jenv
To enable shims and autocompletion add to the botton of your bash_profile file:
Jenv for several Java versions
Get info:
Sample response:
List installers available for use by jenv:
The response:
If you don’t see any, you need to first download a JVM installer containing folders bin, lib, jre, include, bundle, db, man.
The path to a particular version is constructed by adding “/Contents/Home” to the end of the path.
The point of jenv is to add additional versions, such as back version JDK 7.
The response:
Add JDK 8:
http://download.oracle.com/otn-pub/java/jdk/8u101-b13/jdk-8u162-macosx-x64.dmg
The response:
The above provide a handle for jenv provide other apps to use.
List the Java versions jenv knows about:
jenv versions
The response if none if brew cask was not installed:
To configure global version for all apps to use:
Example response:

Open JDK

Open JDK is the open-sourced implementation of the JRE spec, athttp://openjdk.java.net

But some say it is not ready for “prime time” on MacOS because its installation is a dirty affair from 2013 when going from v6 to v7:

https://wiki.openjdk.java.net/display/MacOSXPort/Mac+OS+X+Port+Project+Status

Open JDK’s install page at http://openjdk.java.net/install/shows apt-get (for Debian, Ubuntu) andyum (for Red Hat, CentOS, Oracle Linus, Fedora).

http://blog.shelan.org/2015/03/how-to-build-open-jdk-9-on-mac-osx.htmlon Yosemite
http://hanxue-it.blogspot.com/2014/05/installing-java-8-managing-multiple.html

For macOS, this page recommends using Make to compile from source.

Download source using Mercurial to a new folder “openjdk9”:
hg clone http://hg.openjdk.java.net/jdk9/jdk9 openjdk9cd ./openjdk9
Note JDK 9 is under active development.
http://hg.openjdk.java.net/jdk8/jdk8 work stopped at 2014-03-04.
Install XQuartz for X Window System that runs on Macs:
brew install Caskroom/cask/xquartz brew cask list
NOTE: Downloaded /Library/Caches/Homebrew/xquartz-2.7.9.dmg was 7.9K
xquartz staged at ‘/opt/homebrew-cask/Caskroom/xquartz/2.7.9’ (73M)
cd to the .tar.gz directory containing the configure file for Make to use.
XQuartz fixes an error in this command:
bash ./configure
Install apple-gcc42 the Apple C compiler.
Mihail recommends:
Install ccache (compiler cache):
brew install ccache
Make a symlink /usr/bin/gcc -> /usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/gcc-4.2 (same for g++)

Test JDK Build

https://mihail.stoynov.com/2015/01/29/building-openjdk-9-on-a-osx-or-any-linux/ shows JDK 9 install using ccache, mercurial (hg), jtreg “testing harness”, and Webrev to diff code

Update Java

https://java.com

Which Java You Got?

Apple Java

Different Javas

Latest Version of Oracle Java

Install Jenv to manage multiple Versions of Java

Jenv for several Java versions

Open JDK

Test JDK Build

Update Java

Download Jdk 1.6 For Mac Os X