I would imagine this is a problem with your CLASSPATH settings.
Please check that the directory containing your complied file is included in your classpath.
for example if you have
a file called Test.java
compiled to genetrate Test.class
in directory called c:\javaprojects
Then your classpath must include c:\javaprojects
This is just an example- your own files & directories can have any names you choose.
Also remember that the
java names are case-sensitive.
Check that your source file has a main method.
regards,
Jyotsna