If you don't have admin rights, use the below command to set environment variables for java using the command prompt

setx JAVA_HOME "C:\Program Files\Java\jdk1.8.0"
setx PATH "%PATH%;%JAVA_HOME%\bin";

Modify the environment variable.

setx -m JAVA_HOME "C:\Program Files\Java\jdk1.8.0"
setx -m PATH "%PATH%;%JAVA_HOME%\bin";

Find JDK Installation Directory

First you need to know the installation path for the Java Development Kit.

Open the default installation path for the JDK:

CopyC:\Program Files\Java

There should be a subdirectory like:

CopyC:\Program Files\Java\jdk1.8.0_172

Note: one has only to put the path to the jdk without /bin in the end (as suggested on a lot of places). e.g. C:\Java\jdk1.8.0_172 and NOT C:\Java\jdk1.8.0_172\bin !

Set the JAVA_HOME Variable

Once you have the JDK installation path:

1. Right-click the My Computer icon on your desktop and select Properties.
2. Click the Advanced tab, then click the Environment Variables button.
3. Under System Variables, click New.
4. Enter the variable name as JAVA_HOME.
5. Enter the variable value as the installation path for the Java Development Kit.
6. Click OK.
7. Click Apply Changes.

Note: You might need to restart Windows

The complete article is here, on my blog: Setting JAVA_HOME Variable in Windows.

It doesn't change value in path or java -version doesn't change in current instance of cmd

You have to restart cmd for the changes to take effect as a cmd shell inherits it environment from the parent process.

So what is the correct way to switch between Java versions from the command line?

Use a set of batch files, as follows:

Being a Java developer, I always compile and test my code on different Java versions. But switching between them is a huge problem. So finally I found an easy method to do this. You have to create following batch files and place them in directory you open your command line in or in SYSTEM PATH. You can use you favorite text editor to create these files.

jdk14.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\j2sdk1.4.2_12
echo setting PATH
set PATH=C:\j2sdk1.4.2_12\bin;%PATH%
echo Display java version
java -version

jdk15.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.5.0_12
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.5.0_12\bin;%PATH%
echo Display java version
java -version

jdk16.bat

@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.6.0_11
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.6.0_11\bin;%PATH%
echo Display java version
java -version

Make sure you assign the appropriate JAVA_HOME value in batch files, according to your Java installation. Whenever you want to switch between Java versions, just run the respective batch file and you are done.

Note: JAVA_HOME and the path to java must always refer to the exact same version of the JDK. If you mix them up, unpredictable things will happen!

Source Switch between different JDK versions in Windows | Oracle Pranav's Blog