As per my understanding you want to change the classpath which you have set by command
set classpath=d:java
can be done
in two ways either you can set classpth directly as environment varible by
--> Right click on my computer select advanced options
--> there you will see option as environment variables open that option
--> now you will see multiple variables being set...search for classpath variable if it exist
their edit this variable value by just putting semicolon and write ur full classpath ended by semicolon and save it.
FOR EG:-
variable name:- CLASSAPTH
variable value- .;C:\Oracle\product\10.1.0\Client_2\jdbc\lib\ojdbc14.jar;
Second option is just set your class in command promt as u have set earlier
by opening command prompt
set classpath=C:\Oracle\product\10.1.0\Client_2\jdbc\lib\ojdbc14.jar;
both the method are easy but i would prefer you should go with first one as by doing that you didn't need to set your classpath again and again after you reboot your system or application.