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macOS - How to install Java 17

Could someone please let me know the steps to install Java on a Mac.
I did brew install java
I get this
Warning: openjdk 17.0.1 is already installed and up-to-date.
To reinstall 17.0.1, run:
brew reinstall openjdk
If I do java -version, I get this.
openjdk version "13.0.8" 2021-07-20
If I have navigate to /Library/Java, I have 2 empty directories.
Where is java 17 installed??

In 2023, even if you can use just brew..
brew install openjdk#17
Java will be installed here:
/usr/local/opt/openjdk#17/bin/java
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
...give a try to sdkman, it's far better than brew
curl -s "https://get.sdkman.io" | bash
then open a new shell and try list to see what you could install ;-)
sdk list java
At time of writing you could use:
sdk install java 17.0.4.1-tem
Java will be installed here:
/Users/freedev/.sdkman/candidates/java/17.0.4.1-tem

Java doesn't mind if you install multiple versions. This is often required; java is not backwards compatible (it tries to change little, but e.g. the java8 to java9 transition broke a ton of stuff, much of it needless and much of it not reasonably expectable or fixable by libraries and apps, so a bunch of java apps and libraries only run on java8 - just an example).
So, yes, you have installed JDK17. Also, yes, if you just run java without specifying which one you want, you so happen to get java13 here.
To see all installed javas, you can run:
/usr/libexec/java_home -V
to 'override', you can use something like (depends on which shell you're using on your mac):
export JAVA_HOME=`/usr/libexec/java_home -v 17`
(the backticks mean: Run this then take the output of it and treat that as the 'value' of the expression. here, assign it to the JAVA_HOME env var. -v 17 requests a path to java 17. The -V option lists all and is meant for your eyeballs, not for scripts. The -v option is mostly for scripting, and that's how we're using it here).
JAVA_HOME decides which java is used by some things, but the java you get when you just type java is /usr/bin/java, and that executable is actually just a wrapper that picks a java to run from amongst all installed versions. It uses JAVA_HOME to decide which java to actually run. There are wrappers for all the common commands (javac, too). You can always run e.g. which javac to see what that actually runs; you probably see /usr/bin/javac. Everything in /usr/bin is one of these wrapper thingies that looks at JAVA_HOME and then runs the binary it finds there.

To specify version 17
brew install openjdk#17
Later I add create a link:
sudo ln -sfn /usr/local/opt/openjdk#17/libexec/openjdk.jdk \
/Library/Java/JavaVirtualMachines/openjdk-17.jdk
And use jenv to control which java version to use

To used the version installed by homebrew rather than the one installed by the OS you can get detailed information from homebrew by typing
brew info java
Currently it states
For the system Java wrappers to find this JDK, symlink it with
sudo ln -sfn /opt/homebrew/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
openjdk is keg-only, which means it was not symlinked into /opt/homebrew,
because macOS provides similar software and installing this software in
parallel can cause all kinds of trouble.
If you need to have openjdk first in your PATH, run:
echo 'export PATH="/opt/homebrew/opt/openjdk/bin:$PATH"' >> ~/.zshrc
For compilers to find openjdk you may need to set:
export CPPFLAGS="-I/opt/homebrew/opt/openjdk/include"

For Homebrew, the package that installs the new AdoptOpenJDK is named as temurin. So you need to use below command:
brew install --cask temurin17
If you get any error like temurin cask not available then update brew using below commands:
brew update
brew tap homebrew/cask-versions
To switch quickly between different versions of java add the entries in bashrc as per your jdk versions like:
alias j8="export JAVA_HOME=`/usr/libexec/java_home -v 1.8`; java -version"
alias j17="export JAVA_HOME=`/usr/libexec/java_home -v 17`; java -version"

Steps to install
You asked:
let me know the steps to install Java on a Mac.
Download an installer free-of-cost from vendors such as Adoptium, Azul Systems, Bellsoft, Amazon, Oracle, Microsoft, SAP, and others.
Run installer app.
Quit the installer app when done.
Verify installation by typing on a command-line in Terminal.app:java --version
Delete installer app that you downloaded.
Configure your IDE to use that new Java implementation you installed.
Java location
You asked:
Where is java 17 installed??
/Library/Java/JavaVirtualMachines/
In the Finder, choose Go > Go to Folder, and paste /Library/Java/JavaVirtualMachines/.
Note that this is not the Library folder within your home folder. We are not referring to /Users/your_user_name/Library/…. We are referring to the root Library folder that applies across all the user accounts on this Mac.
You said:
I did brew install java
No need for the Homebrew package manager. If you already enjoy using the brew tool, proceed. But if new to Homebrew, skip it if your only goal is to install Java. Just use an installer for Java as you would for many Mac apps.
JavaFX
You added a tag for javafx.
Be aware that for JavaFX, you have two options:
Include the necessary OpenJFX libraries within your development project and within your final app, or …
Use a JDK that includes the JavaFX/OpenJFX libraries.
At least two vendors provide JDK installers that include the JavaFX/OpenJFX libraries:
Azul Systems (ZuluFX)
Bellsoft (LibericaFX)

This answer is specifically if you use Intellij on a Mac
Within IntelliJ, you can use the IDE to add new JDKs of selected versions from common vendors. Instructions for this are here:
Setup the project JDK
When setting up the JDK, you can either:
Select a pre-existing JDK which has been registered with the IDE OR
Use the Add JDK option to add a new JDK which you previously downloaded and installed using the method outlined in Basil's answer OR
Use the Download JDK option to choose a vendor and version of the JDK that the IDE will automatically download, install and make available for selection.
The JDKs installed by Idea will be located in the same location as outlined in Basil's answer for a manual install /Library/Java/JavaVirtualMachines/.
One common issue is that the version of the JDK registered for the project differs from the default version used in the terminal. This can sometimes mean that the app works when run in Idea, then fails when run in the terminal (or, at least that it is executed against a version of the JDK you didn't expect).
To select the version of the JDK to run in the terminal, configure the Java home setting as outlined in rzwitserloot's answer.
export JAVA_HOME=`/usr/libexec/java_home -v 17`
Also, some tools such as the openjfx maven plugin will not use the java version selected in Idea when executing a call to a JDK tool like jlink, but will instead have their own mechanism for finding a JDK to use (e.g. look at JAVA_HOME or use the Maven toolchains plugin). So it is always good to check the JAVA_HOME variable and ensure that it is set to a reasonable value, both for terminal execution and for effective use of Java development tools that may rely on it.

I think that answers here are not fully out of topic, but from my point of view, my case is exactly the same as that of the author. I had already installed java 8, 11, and 13. All of them resides at:
/Library/Java/JavaVirtualMachines/
Nevertheless when I tried to find the path of JDK 17 it resides:
/usr/local/Cellar/openjdk
I use Mac OS Big Sur and the JDK was installed with homebrew

Brew now supports searching old formulae and allowing you to install a specific version. I'm using Homebrew 3.5.2-117-gb941470
Create a local tap: brew tap-new --no-git local/openjdk
Ask Brew to find the formulae of the version you want: brew extract --version 17.0.2 openjdk local/openjdk
Install Java 17 using your new local tap: brew install openjdk#17.0.2
Link the JDK into the MacOS JVM Dir: sudo ln -sfn /usr/local/opt/openjdk#17.0.2/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk17.0.2.jdk
Check Java 17 is available: /usr/libexec/java_home -V
Set Java Home: export JAVA_HOME=$(/usr/libexec/java_home -v17)
Check current version of Java is correct...
$ java --version
openjdk 17.0.2 2022-01-18

The following method installs Java without the need for any additional tools or package managers.
Go to https://jdk.java.net/17/ and download the latest macOS archive.
Download the latest Adoptium release for the Java 17 branch by going to https://adoptium.net/temurin/releases/ and be sure to select the tar.gz version.
The archive is either for x64 (Intel CPU) or for AArch64 (Apple Silicon / M1 CPU).
Then, open a Terminal, and extract the downloaded archive to the system path for Java virtual machines:
cd Downloads
tar xzf OpenJDK17U-jdk_aarch64_mac_hotspot_17.0.5_8.tar.gz -C /Library/Java/JavaVirtualMachines

What is the proper way of using JDK on WSL2 on Windows 10?

I have installed Ubuntu 20.4 LTS on WSL. My windows 10 already have the JDK installed. Do I need to install JDK on ubuntu on WSL or can I use the Windows 10 JDK in the Ubuntu? How you do Java programming on WSL? Which is the proper way?
I was just wondering if I need to install all the development tools and binaries again on Linux won't it take a lot of space & hog a lot of CPU/Ram resources?

Run the following commands as a user with sudo privileges or root to update the packages index and install the OpenJDK 11 JDK package:
$ sudo apt update
$ sudo apt install openjdk-11-jdk
Once the installation is complete, you can verify it by checking the Java version:
$ java -version
The output should look something like this:
openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment (build 11.0.7+10-post-Ubuntu-3ubuntu1)
OpenJDK 64-Bit Server VM (build 11.0.7+10-post-Ubuntu-3ubuntu1, mixed mode, sharing)
Set JAVA_HOME Environment Variable:
OpenJDK 11 is located at /usr/lib/jvm/java-11-openjdk-amd64/bin/java
Once you found the path of your preferred Java installation, open the /etc/environment file:
$ sudo nano /etc/environment
Assuming you want to set JAVA_HOME to point to OpenJDK 11, add the following line, at the end of the file:
JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"
For changes to take effect on your current shell you can either log out and log in or run the following source command:
$ source /etc/environment
Verify that the JAVA_HOME environment variable was correctly set:
$ echo $JAVA_HOME
You should see the path to the Java installation:
/usr/lib/jvm/java-11-openjdk-amd64
for reference you can follow this link below
How to Install Java on Ubuntu 20.04

We can use that Windows JDK inside the wsl2. we should add this to /etc/environment
JAVA_HOME=/mnt/c/Program Files/Java/jdk-11.0.8/bin/
by adding this bin folder we may run regular commands but append with .exe format eg: javac.exe hello.java java.exe hello.java
if you don't like that way then add alias like below:
alias java='java.exe'
alias javac='javac.exe'
I think we can use any of the windows programs like this :)

There is not a "proper" (as in supported or recommended by JDK providers) way to install or use Java on WSL. I could not find any official recommendations.
However, it is possible to either install and use Oracle JDK for Windows installation from WSL, or install OpenJDK Java into your WSL world from the Ubuntu package manager.
I was just wondering if I need to install all the development tools and binaries again on Linux won't it take a lot of space & hog a lot of CPU/Ram resources ?
See above. But note that you are only going to "hog CPU/RAM" if you are running both kinds of JVM at the same time.
References:
Installing Oracle JDK on Windows subsystem for Linux
Java JDK 11 install script for Windows Subsystem for Linux (WSL)
Windows Subsystem for Linux Java Setup ... using the Ubuntu package system.
(There are many more articles on this topic if the above don't address your concerns.)

I installed Java via IntelliJ IDEA on Windows 11 and wanted to reuse the installation on WSL.
Create matching functions in ~/.bashrc to start the executables directly and export them so they can be used from subshells:
java() {
/mnt/c/Program\ Files/Eclipse\ Adoptium/jdk-<version>/bin/java.exe "$#"
}
export -f java
javac() {
/mnt/c/Program\ Files/Eclipse\ Adoptium/jdk-<version>/bin/javac.exe "$#"
}
export -f javac

As400 run a personal JRE

i have a java program that must run on an as400, running it from qshel run jre 1.6, but my dependencies require jre 1.8 is it possible to start that program with portable 1.8 jre?
as is also done on Windows and Linux with the .bat and .sh files!
can you tell me the commands to customize the (java home) without moving the 1.6 installed?

Traditionally, the only JVMs available for the IBM i platform come from IBM. These are available through various options of the 5770-JV1 product. Versions up to 1.8 are available for IBM i 7.1 and up (perhaps earlier, but I haven't gone digging) You can find the available JVM options at https://www.ibm.com/support/pages/node/1117869
To use a Java 1.8 64-bit VM from QSH, you could do eg.
JAVA_HOME=/QOpenSys/QIBM/ProdData/JavaVM/jdk80/64bit
export JAVA_HOME
java -jar ...

Your challenge is a very common task in legacy systems.
This worked for me:
Put your portable jre.zip close to your java program.
Unzip it
Create a JAVA_HOME just for this execution:
export JAVA_HOME=/home/mydownloads/jre
export PATH=${PATH}:$JAVA_HOME/bin
Try with java -version
Execute your java program: java -jar myapp.jar
You could add this steps to yous bash scripts.

javac : command not found

I have installed java in my CentOS release 5.5 machine using the command yum install java. But I am unable to compile a class using javac.
Do I need to install any other package?
I have tried to locate the javac executable but i am unable to locate it.
/usr/bin/java is linked as follows:
/usr/bin/java -> /etc/alternatives/java
/etc/alternatives/java -> /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
I have seen the following output by yum list installed |grep java:
java-1.6.0-openjdk.x86_64 1:1.6.0.0-1.16.b17.el5 installed
tzdata-java.x86_64 2011b-1.el5 installed

Worked for me with this command:
yum install java-devel

You installed the Java Runtime Environment (JRE) only, which does not provide javac. For javac, you have to install the OpenJDK Development Environment. You can install java-devel or java-11-devel, which both include javac.
By the way: you can find out which package provides javac with a yum search, e.g.
su -c 'yum provides javac'
on more recent releases of CentOS e.g. 6 the command changes to
su -c 'yum provides */javac'

Use the following sudo command:
sudo yum install java-1.6.0-openjdk-devel

I don't know exactly what yum install java will actually install. But to check for javac existence do:
> updatedb
> locate javac
preferably as root. If it's not there you've probably only installed the Java runtime (JRE) and not the Java Development Kit (JDK). You're best off getting this from the Oracle site: as the Linux repos may be slightly behind with latest versions and also they seem to only supply the open-jdk as opposed to the Oracle/Sun one, which I would prefer given the choice.

I use Fedora (currently 31)
Even with JDK's installed, I still need to specify JAVAC_HOME in the .bashrc, especially since I have 4 Java versions using sudo alternatives --configure java to switch between them.
To find java location of java selected in alternatives
readlink -f $(which java)
In my case:
/usr/java/jdk1.8.0_241-amd64/jre/bin/java
So I set following in .bashrc to:
export JAVA_HOME=/usr/java/jdk1.8.0_241-amd64/jre/bin/java
export JAVAC_HOME=/usr/java/jdk1.8.0_241-amd64/bin/javac
export PATH=$PATH:/usr/java/jdk1.8.0_241-amd64/jre/bin
export PATH=$PATH:/usr/java/jdk1.8.0_241-amd64/bin/
Now javac –version gives:
javac 1.8.0_241
This is useful for those who want to use Oracle's version. Just remember to change your .bashrc again if you make a change with java alternatives.

Is the javac executable in a directory that is part of your PATH?
I don't know the CentOS equivalent of the Windows path but if you cd to the java sdk directory and run ./javac does anything happen?

Install same version javac as your JRE
yum install java-devel

This worked for me:
sudo dnf install java-<version>-devel

You have installed the Java Runtime Environment(JRE) but it doesn't contain javac.
So on the terminal get access to the root user sudo -i and enter the password.
Type yum install java-devel, hence it will install packages of javac in fedora.

Linux Mint 19.3
I installed Java Oracle manually, like this:
$ sudo ln -s /usr/lib/jvm/java-1.8.0_211/bin/javac /usr/bin/javac

for java 8 use
sudo yum install java-1.8.0-openjdk-devel

Make sure you install JDK/JRE first.
follow these steps:
open terminal go to your root dictionary by typing
cd /
you will see Library folder
Now follow this path Library/Java/JVM/bin
Once you get into bin you can see the javac file
Now you need to get the path of this folder for that just write this command
pwd
get the path for your javac.

JVM version manager

Is there Ruby Version Manager equivalent for the Java world?
I'm looking for tool which allow me to easily download and install a new JVMs and switch between them. For example:
jvm install <version>
jvm list //will list installed JVMs on my system
jvm use jdk1.6 //will switch my env to jdk 1.6 version, etc.

http://www.jenv.be/ will allow this type of control.

SDKMAN! is a similar tool for the Java ecosystem. Supports various Java versions, Scala, Clojure, Kotlin, Groovy, and build tools like Maven and Gradle.
Works on Mac and Linux, with some mentions of support for Windows depending on how hard you are willing to try :)

If you use Ubuntu you can specify which JVM you want to use via command (works only for JVM installed from apt-get or aptitude)
sudo update-alternatives --config java
Or by setting JAVA_HOME. Here is good tutorial:
http://vietpad.sourceforge.net/javaonlinux.html

For the sake of completeness, there are two more - jabba (of which I am the author; written in Go and designed after nvm/gvm/rvm) and jenv (not to confuse with jenv.be; doesn't support installation from oracle but can install from a custom zip).

With JVMs, if you need to switch between them you just need to use a batch file (or powershell script) to manage the classpath and JVM path. You don't need to rely on the system default JVM path and instead just allow your app to point to whatever JVM you like by changing classpath and JVM path environment in the shell that runs the JVM.
For programs that are getting Java location from the Registry, in theory you could use a batch script to update that also.
In this respect Java is way easier than "Ruby version manager".

As it is not (yet) in the list of possibilities, there's also asdf.
asdf does not only provide version management for java, it has plugins for ~400 different languages and tools by default, you can find more on github, or create your own.
Here is an example how to setup a new install (you can also install completion so you don't have to list the versions first). The java plugin is added, a specific version (there are versions for adoptopenjdk, corretto, dragonwell, graalvm, liberica, mandrel, microsoft, openjdk, oracle, sapmachine, semeru, temurin, trava, zulu) is installed and configured to be the global (or local version) to use:
asdf plugin-add java # Add java Plugin
asdf list-all java # List all available java versions
asdf install java openjdk-18 # Install specific jdk version
asdf install java openjdk-17 # Install another jdk version
asdf global java openjdk-18 # Set the global jdk version
asdf local java openjdk-17 # Set the local version for calls from the current directory
asdf uses a file in $HOME/.tool-versions to configure the global selected version. If you call any tool in a directory that has a .tool-versions file with a different version, that one is used (defined with asdf local …).

The trick is to use update-java-alternatives (from the java-common package). The update-alternatives command will not update every one of the symbolic links for various java /bin executables, which is why update-java-alternatives is better.
So to go for OpenJDK 6 to 7, use update-java-alternatives -l to get a list of Java alternatives and then used sudo update-java-alternatives -s java-1.7.0-openjdk-amd64 to switch the JDK.
CAVEAT: The command above might throw the following errors,
update-alternatives: error: no alternatives for mozilla-javaplugin.so.
update-java-alternatives: plugin alternative does not exist:
/usr/lib/jvm/java-7-openjdk-amd64/jre/lib/amd64/IcedTeaPlugin.so
This is because the openjdk plugin is not installed by default. To fix run sudo apt-get install icedtea-7-plugin and rerun update-java-alternatives.