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.

Understanding class path wildcards

Class path entries can contain the basename wildcard character , which is considered equivalent to specifying a list of all the files in the directory with the extension .jar or .JAR. For example, the class path entry foo/ specifies all JAR files in the directory named foo. A classpath entry consisting simply of * expands to a list of all the jar files in the current directory.

A class path entry that contains * will not match class files. To match both classes and JAR files in a single directory foo, use either foo;foo/* or foo/*;foo. The order chosen determines whether the classes and resources in foo are loaded before JAR files in foo, or vice versa.

Subdirectories are not searched recursively. For example, foo/* looks for JAR files only in foo, not in foo/bar, foo/baz, etc.

Must read full detail here, it is awesome http://docs.oracle.com/javase/6/docs/technotes/tools/windows/classpath.html

I'm not a Java programmer, so I don't know the correct value for CLASSPATH. But, you seem to. You can add it to ~/.bashrc like so:

CLASSPATH=/path/to/1:/path/to/2:/etc

The change will take effect globally the next time you log in. However, it will take effect immediately in new shells.

Additionally, if you want to set it for just one particular command, do this:

CLASSPATH=/something command-here arg1 arg2

A third way would be to create a wrapper script, which would be appropriate if you needed to set multiple variables or if you needed to determine appropriate values programmatically:

#!/bin/bash
export CLASSPATH=/something
export ANOTHER_ENV_Variable=foo

exec your_fancy_program "$@"