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 FilesJavajdk1.7.0_51bin
    4. Paste it after putting a semi-colon(;) in value section 

i am getting below error while running java in cmd

C:UsersUser>java -version
Error: opening registry key 'SoftwareJavaSoftJava Runtime Environment'
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.

Answer

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.