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Change system Java

I have 3 java in my system 1.6, 1.7 and java 8.
I set my JAVA_HOME and path to 1.7, but when I run java -version using cmd administrator mode it return me 8.
Could anyone please tell me from where cmd pick java, and how i can change it to another version.
Updated: I already set java 7/bin in path variable

Start your cmd shell and type echo %PATH%.
OS would inspect listed directories and the first one that has java binary will be the one being used.
To change it - the PATH variable is set based on the settings in Control Panel -> System -> Advanced System Settings -> Environment Variables. You'd need to start a new cmd session to see updated changes.

When we run cmd as an administrator then it pick java.exe which is already available under C:/user/windows32 folder.
To resolve this issue, instead of appending my java at the end of the path, append in the starting of the path vaiable.
So here is the code used in cmd if run as administrator
set path=%JAVA_HOME%/bin;%path%;
java -version

How to install java 7 on mac in custom location?

I want to install java 7 on mac silently. I am unable to find any documentation/links on the same. Also I don't want it in /Library. Is it possible to install the same on any custom location. I am very new to mac any help is highly appreciated.

Just to make the steps from #HawkMage more explicit (and illustrate them working with JDK8):
Download the binary (eg, jdk-8u5-macosx-x64.dmg) from Oracle
Double click from Finder to mount the Volume. Ignore the window with the “JDK 8 Update x.pkg”
Use pkgutil to expand the contents of the package into a temporary directory:
$ pkgutil --expand /Volumes/JDK\ 8\ Update\ 05/JDK\ 8\ Update\ 05.pkg /tmp/jdkpkg
Then, change to that dir and use cpio to expand the Payload file:
$ cd /tmp/jdkpkg
$ cpio -i < ./jdk18005.pkg/Payload
Finally, move the Home dir to wherever you’d like your JAVA_HOME to live
$ mv Contents/Home /mytools/jdk-1.8.0_05

Unfortunately the "standard" Java that comes on OS X is packaged in a very non-standard way.
It is not as easy as linux, the DMG downloaded gives you a PKG file that if you run it just installs Java. This is not useful if you are trying to keep the standard Java that comes with OS X intact.
What I do is download the DMG file from Oracle and open it but instead of running the PKG I use pkgutil to extract the contents of the package. You will find a directory named jdk*.pkg and in it you will see a file named Payload. This is a GZipped CPIO file and you can extract it by cating it and piping it into cpio -zi. From this you will now have a directory named Contents and under it you will find a directory named Home. This "Home" directory is the what you would normially get with the Linux tar.gz Java download. You can copy it to wherever you want and put the bin directory in your path and set the JAVA_HOME to it and you are good to go.

Just like in Linux, you can pretty much install Java anywhere you like on a mac. You just need to make sure that you add the Java executable to the path or create a symbolic link of the java executable and put it in the /usr/bin/ directory so it can be executed anywhere.
To add Java to path:
1) Modify .bash_profile found in your home director.
2) Add this line: export PATH=/yourjavadir/bin:$PATH
3) Save and exit
4) Then do source .bash_profile to reload the file. You'll only need to do this one time.
To create a symbolic link:
ln -s /yourjavadir/java /usr/bin/java

I had the same issue and just managed to figure it out.
Download and unzip the Java binary in your custom directory. For eg -
/Users/myuser/Documents/jre1.8.0_25.jre
Update your .bash_profile with the following parameters
export JAVA_HOME=/Users/a514624/Documents/jre1.8.0_25.jre/Contents/Home
export PATH=$PATH:$JAVA_HOME/bin
Close the terminal window and open it again. Alternately, you could type the command 'source .bash_profile'.
After these steps, if you type java -version on the command prompt, you would see it reflecting the version which you were hoping to see -
$ java -version
java version "1.8.0_25" Java(TM) SE Runtime
Environment (build 1.8.0_25-b17) Java HotSpot(TM) 64-Bit Server VM
(build 25.25-b02, mixed mode)
Unlink the existing Java softlink (would require root/elevated privileges)
root$ unlink /usr/bin/java
Create a symbolic link to the new Java installation
root$ ln -s /Users/myuser/Documents/jre1.8.0_25.jre/Contents/Home/bin/java /usr/bin/java
Thats it. Life is beautiful after this. Hope this helps!

If you just need JRE/Java Runtime Edition then previous answers arecorrect but if you need JRE and JDK (Java Development Kit) then simply go to below link and select the mac and run the dmg and it's much better and by far the easiest.
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

How to change the default compiler?

I have javac complier installed on my mac mashine. By default its version is 7. I want to set complier version to 6 by default. How do I do it on Mac?
Ive found simular solution for ubuntu:
http://bartling.blogspot.com/2007/03/getting-java-6-to-be-default-jvm-on.html

$ export JAVA_HOME=/usr/libexec/java_home -v '1.6*'

Run a command which exports your configuration:
export JAVA_HOME=/usr/libexec/java_home -v '1.6*'
This would last only until you restart your computer, so be sure to include it to your configuration as well. I'm not an OSX user so I'm not sure how exactly is the file called, but it's basically and equivalent of ".bashrc" on Linux. Just put the export line on the end of the file, so it will export it every time in future. (It's probably the same file because they're both UNIX based)

"java -version" not working in command prompt

I downloaded this Java JDK and installed it.
But when I go to the command prompt to check the version, it says it's not recognized.
Is anyone else experiencing this issue with the latest Java?
I might not have installed the right version. I need the java that works with grails
C:\>java
'java' is not recognized as an internal or external command,
operable program or batch file.
C:\>java -version
'java' is not recognized as an internal or external command,
operable program or batch file.
C:\>
when i do a search on my computer for java, it does not find anything

Windows 2k8 R2 server-
For both java [-option] or %JAVA_HOME% to work in the command line you need the following:
In Control Panel->System and Security->System->Advanced system setting->Advanced->Environment Variables->System Variables
Edit the Path variable and add a ";" after the last value and add the the path to the Java bin directory:
e.g.- C:\Progra~2\Java\jre6\bin\
Add the JAVA_HOME Variable with the value set to the path for the java executable:
e.g.- C:\Progra~2\Java\jre6\bin\java.exe

Press simultaneously the "windows" and "pause" buttons on your keyboard, this will bring up the System Preferences dialog.
In the Advanced tab, find Environment Variables.
Then, in the User (upper) section, create or update the following two variables :
JAVA_HOME = where you put your JDK, eg. C:/Java/SDK
PATH = %JAVA_HOME%/bin
Close the dialogs.
Then, in a new command-line console, try "javac -version" and see if it's detected.
It's important that you use a new console, because environment variables are read only when the console is launched.

Java is typically installed (on Windows) as C:\Program Files\Java\jdk<version>
That installation directory has a subdirectory bin which you need to append to your PATH environment variable via the control panel. Then, the commands like java, javac etc. will be available on the command line.
BTW, the same is true for Grails.

Is the -version flag not recognized, or is the "java" command not recognized? One way to test this is just to type 'java' by itself and run it and see what happens.
If the command is not recognized, make sure that the JDK's install path is in your windows PATH. If not, you won't be able to use any of the java executables from the command prompt. Here's another link that may help out.

You need to manually add the path to javac.exe and java.exe to your operating system path. The Java installation program doesn't do that for you.

You most likely don't have java.exe in your system's PATH variable.

For Linux:
check $PATH and $JAVA_HOME. You can configure it in /etc/environment
From console you can check it like:
$ echo $PATH
For Windows:
My Computer -> Properties -> Advanced -> Environment Variables
Check there PATH.
From console you can check it like:
echo %PATH%

You should have a Java icon in Windows Control Panel. Locate the Java tab and click the View button. That will show you the path to the Java executables.
Last but not least, make sure you have restarted the computer so changes in the PATH variable can take effect.

You installed the JDK. Isn't java.exe part of the JRE? Do you have that installed?

Maybe your system variables in the environment variables are not set properly. Follow the steps in the link below. Finally, make sure the path component in system variables has only one JDK path. Delete other JDK paths that you won't use.
https://docs.oracle.com/javase/tutorial/essential/environment/paths.html

You might have installed a previous or older version of Java so you can just uninstall it and directly download JDK from Java JDK
I was also facing the same issue but when I downloaded and installed the latest version the issue was resolved.
Also uninstall any other Java versions which may be present in the program files.
To get to know other versions which may be present in your computer use Windows File Explorer to go to:
Files > Windows C > Program Files > Java
All the JDK and JRE you have will be listed there. Uninstall any other Java versions other than what you installed. And then make sure you have set the path variable of the JDK.

For me, it was incorrect line in the PATH
(1) Check PATH: Type "Edit System Environment Variables" on the search -> System Properties -> Advance -> Environment Variables -> System variables -> Path
(2) On the list, mine was C:\Program Files (x86)\Common Files\Oracle\Java\javapath so I just add \ at the end (the exe files in the javapath folder)
OS: Windows 10 64 bit

IF you set the PATH and it's not showing up in cmd when you run %PATH%, try restarting your computer.

What should I set JAVA_HOME environment variable on macOS X 10.6?

Many Java applications that use shell scripts to configure their environment use the JAVA_HOME environment variable to start the correct version of Java, locate JRE JARs, and so on.
In macOS X 10.6, the following paths seem to be valid for this variable
/Library/Java/Home
/System/Library/Frameworks/JavaVM.framework/Home
/System/Library/Frameworks/JavaVM.framework/Versions/Current
Some of these are symlinks to the actual current VM (as defined in the Java Preference pane).
But which one should be used—or is it okay to use any of them?

I just set JAVA_HOME to the output of that command, which should give you the Java path specified in your Java preferences. Here's a snippet from my .bashrc file, which sets this variable:
export JAVA_HOME=$(/usr/libexec/java_home)
I haven't experienced any problems with that technique.
Occasionally I do have to change the value of JAVA_HOME to an earlier version of Java. For example, one program I'm maintaining requires 32-bit Java 5 on OS X, so when using that program, I set JAVA_HOME by running:
export JAVA_HOME=$(/usr/libexec/java_home -v 1.5)
For those of you who don't have java_home in your path add it like this.
sudo ln -s /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java_home /usr/libexec/java_home
References:
Oracle explains the java_home command
An article for configuring the JDK in Spring Tool Suite (Eclipse
2019) on MacOS

Also, it`s interesting to set your PATH to reflect the JDK. After adding JAVA_HOME (which can be done with the example cited by 'mipadi'):
export JAVA_HOME=$(/usr/libexec/java_home)
Add also in ~/.profile:
export PATH=${JAVA_HOME}/bin:$PATH
P.S.: For OSX, I generally use .profile in the HOME dir instead of .bashrc

I am having MAC OS X(Sierra) 10.12.2.
I set JAVA_HOME to work on React Native(for Android apps) by following the following steps.
Open Terminal (Command+R, type Terminal, Hit ENTER).
Add the following lines to ~/.bash_profile.
export JAVA_HOME=$(/usr/libexec/java_home)
Now run the following command.
source ~/.bash_profile
You can check the exact value of JAVA_HOME by typing the following command.
echo $JAVA_HOME
The value(output) returned will be something like below.
/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home
That's it.

I'm on Mac OS 10.6.8
The easiest solution works for me is simply put in
$ export JAVA_HOME=$(/usr/libexec/java_home)
To test whether it works, put in
$ echo $JAVA_HOME
it shows
/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
you can also test
$ which java

Nowadays Java seems to be installed in /Library/Java/JavaVirtualMachines

I tend to use /Library/Java/Home. The way the preferences pane works this should be up to date with your preferred version.

That above works not any more in YOSEMITE for GRAPHICAL APPLICATIONS! Like eclipse, or anything started with Spotlight. (.bash_profile, launchd.conf works for terminal sessions only.)
Before starting eclipse, just open a terminal window, and give out the following command:
launchctl setenv JAVA_HOME /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home
(With your installation path! Perhaps works with $(/usr/libexec/java_home) instead of the full path too.)
View the whole excellent article about the permanent solution here:
Setting environment variables via launchd.conf no longer works in OS X Yosemite/El Capitan/macOS Sierra?

It is recommended to check default terminal shell before set JAVA_HOME environment variable, via following commands:
$ echo $SHELL
/bin/bash
If your default terminal is /bin/bash (Bash), then you should use #hygull method
If your default terminal is /bin/zsh (Z Shell), then you should set these environment variable in ~/.zshenv file with following contents:
export JAVA_HOME="$(/usr/libexec/java_home)"
Similarly, any other terminal type not mentioned above, you should set environment variable in its respective terminal env file.
This method tested working in macOS Mojave Version 10.14.6.

I've found this stack to help, i was having the same issue and i could fix:
My java path was here:
/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home
and was needed to put into my .bash_profile:
export JAVA_HOME=\"/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home\"
Hope help

As other answers note, the correct way to find the Java home directory is to use /usr/libexec/java_home.
The official documentation for this is in Apple's Technical Q&A QA1170: Important Java Directories on OS X: https://developer.apple.com/library/mac/qa/qa1170/_index.html

For me maven seems to work off the .mavenrc file:
echo "export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)" > ~/.mavenrc
I'm sure I picked it up on SO too, just can't remember where.

Create file ~/.mavenrc
then paste this into the file
export JAVA_HOME=$(/usr/libexec/java_home)
test
mvn -v

Skipping Terminal setup since you mentioned applications, permanent system environment variable set up (works for macOS Sierra; should work for El Capitan too):
launchctl setenv JAVA_HOME $(/usr/libexec/java_home -v 1.8)
(this will set JAVA_HOME to the latest 1.8 JDK, chances are you have gone through serveral updates e.g. javac 1.8.0_101, javac 1.8.0_131)
Of course, change 1.8 to 1.7 or 1.6 (really?) to suit your need and your system

For Fish Shell users, use something like the following: alias java7 "set -gx JAVA_HOME (/usr/libexec/java_home -v1.7)"