Do I need to restart my system after setting JAVA in system environment's path variable?

I did the following steps but java does not seem to be working for me, do I need to restart my system if yes then why?

1. Right click My Computer->Advence Option->Environment Varibles->System Variables 
    2. variable : Path->Edit
    3. Copy your jdk bin directory i.e.C:\Program Files\Java\jdk1.7.0_51\bin
    4. Paste it after putting a semi-colon(;) in value section

i am getting below error while running java in cmd

C:\Users\User>java -version
Error: opening registry key 'Software\JavaSoft\Java Runtime Environment'
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.

No, but you will need to close and recreate any cmd windows, running java programs, or the like.

To check it's correct, open a new cmd window and type set -> review the information for PATH and JAVA_HOME.

You should set two things:

JAVA_HOME
PATH

The first lies under the "User variables for [your user name]" section. Add the JAVA_HOME variable and set it to where your jdk is installed. i.e. C:\Program Files\Java\jdk1.7.0_51\

The second lies under the "System variables" section. You should find the "path" variable, and edit it. Then, append ";%JAVA_HOME%\bin" (minus the quotes) to the end of the path variable.

After you have done this, save the variables and close that window clicking the "ok" button. Close down all instances of the command prompt (and any IDE you may be developing with such as Eclipse or NetBeans), and reopen one command prompt. Then, if you would like to test whether or not your changes worked and are in effect, try the following:

echo %JAVA_HOME%

This should output where you set your java home variable to.

echo %PATH%

At the end of what is output, you should see your java home\bin addition to the path variable

java -version

If you can run this command from the command line, it means that your environment was set up correctly and java is now in your path.

SparkOn

Not necessary. Reopen a command prompt (if any) that runs the java process and type java -version to check if it installed successfully.

NO.
You don't need to restart the system, but just the application like cmd or any IDE you are using for java development (i.e Eclipse) need to restart.

And to confirm that the java path is set that you have mentioned in JAVA_HOME environment variable, you can open cmd and you can check with commands echo %JAVA_HOME% or echo %PATH%.

Sayed Naweed

No, you don't need to restart your system. However, you have to restart your command prompt application to update the changes done on Environment variables.

Sandeep vashisth

I reinstall the JDK and set the JAVA_HOME and PATH variable again. now it's working.

In my case under user variable section(for particularuser) JAVA_HOME set to jre not jdk path . I change it to JDK path , It worked for me

来源：https://stackoverflow.com/questions/24307782/do-i-need-to-restart-my-system-after-setting-java-in-system-environments-path-v

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