This answer is an attempt to address: how to control java version system-wide (not just in currently running shell) when several versions of JDK are installed for development purposes on macOS El Capitan or newer (Sierra, High Sierra, Mojave). As far as I can tell, none of the current answers do that (*).

As a developer, I use several JDKs, and I want to switch from one to the other easily. Usually I have the latest stable one for general use, and others for tests. But I don't want the system (e.g. when I start my IDE) to use the latest "early access" version I have for now. I want to control system's default, and that should be latest stable.

The following approach works with Java 7 to 12 at least (early access at the time of this writing), with Oracle JDK or OpenJDK (including builds by AdoptOpenJDK produced after mid-October 2018).

Solution without 3rd party tools:

• leave all JDKs at their default location, under /Library/Java/JavaVirtualMachines. The system will pick the highest version by default.
• To exclude a JDK from being picked by default, rename its Contents/Info.plist to Info.plist.disabled. That JDK can still be used when $JAVA_HOME points to it, or explicitly referenced in a script or configuration. It will simply be ignored by system's java command.

System launcher will use the JDK with highest version among those that have an Info.plist file.

When working in a shell with alternate JDK, pick your method among existing answers (jenv, or custom aliases/scripts around /usr/libexec/java_home, etc).

Details of investigation in this gist.

(*) Current answers are either obsolete (no longer valid for macOS El Capitan or Sierra), or only address a single JDK, or do not address the system-wide aspect. Many explain how to change $JAVA_HOME, but this only affects the current shell and what is launched from there. It won't affect an application started from OS launcher (unless you change the right file and logout/login, which is tedious). Same for jenv, it's cool and all, but as far as I can tell it merely changes environment variables, so it has the same limitation.

Use

sudo update-alternatives --config java

which lists all installed versions with current active one marked and provides dialog to switch:

There are 3 choices for the alternative java (providing /usr/bin/java).

Selection    Path...
------------------------------------------------------------
  0            /usr/lib/jvm/java-9-oracle/bin/java...
* 1            /usr/lib/jvm/java-7-oracle/jre/bin/java...
  2            /usr/lib/jvm/java-8-oracle/jre/bin/java...
  3            /usr/lib/jvm/java-9-oracle/bin/java...

Press <enter> to keep...[*], or type selection number: 

Use

export JAVA_HOME="$(jrunscript -e 'java.lang.System.out.println(java.lang.System.getProperty("java.home"));')"

to set $JAVA_HOME from current active version

In the command shell:

set JAVA_HOME=C:\jdk1.6.0u24
set PATH=%JAVA_HOME%\bin;%PATH%

That will temporarily set up the environment in the command shell. Maven, Ant, etc. will pick up on your new version of Java without having to go to the Control Panel repeatedly.

Tools like Eclipse should be able to select which JDK to use in their own configuration tools for use within their environments.

In case if someone want to switch frequently in each new command window then I am using following approach.

Command Prompt Version:

Create batch file using below code. You can add n number of version using if and else blocks.

@echo off
if "%~1" == "11" (
   set "JAVA_HOME=C:\Software\openjdk-11+28_windows-x64_bin\jdk-11"
) else (
   set "JAVA_HOME=C:\Program Files\Java\jdk1.8.0_151"
)
set "Path=%JAVA_HOME%\bin;%Path%"
java -version

Save this batch file as SJV.bat and add this file location in your machine's Path environment variable. So now SJV will act as command to "Switch Java Version".

Now open new command window and just type SJV 11 it will switch to Java 11. Type SJV 8 it will switch to Java 8.

PowerShell Version

Create powershell(ps1) file using below code. You can add n number of version using if and else blocks.

If($args[0] -eq "11")
{
    $env:JAVA_HOME = 'C:\Software\openjdk-11+28_windows-x64_bin\jdk-11'
}else{
    $env:JAVA_HOME = 'C:\Program Files\Java\jdk1.8.0_151'
}
$env:Path = $env:JAVA_HOME+'\bin;'+$env:Path
java -version

Save this script file as SJV.ps1 and add this file location in your machine's Path environment variable. So now SJV will act as command to "Switch Java Version".

Now open new powershell window and just type SJV 11 it will switch to Java 11. Type SJV 8 OR SJV it will switch to Java 8.

I hope this help someone who want to change it frequently.