Path Environment Variable Setting.

first you must install the jdk in your system.How we install jdk  click here.
if you save your program in bin folder of the jdk ,there is no need to set the path but if you want to save your program in another drive  you must  set the path first.

setting the path permanently through My computer.

open the properties of My computer....
you will get this window...
                                         

click on Advanced window setting

click on Environment  Variables

in user variables click on NEW

in this write:

Variable name:path
Variable value:path of the bin folder of jdk.

Example:-

click ok
now you are ready to run the programs.