EXECUTION PROBLEM

I've problem regarding executing a java program.

The following is the java program:

class Sample

{

public static void main(String args[])

{

System.out.println("Hello World!!");

}

}

The above program is saved as Sample.java and then compiled thru the command:javac Sample.java

Compilation successful;a .class file generates: Sample.class

But when I execute it by the command: java Sample

the following error message appears:

Exception in thread 'main' java.lang.NoClassDef Found. Error:Sample

I know that it is a runtime environment variable problem or something like that.But I don't know how to fix it. I've installed and then uninstalled and and again reinstalled to get rid of it.But all in vain.

PLEASE SUGGEST A SOLUTION HOW TO SOLVE THIS PROBLEM.

THANKS

[868 byte] By [Cyrus_71a] at [2007-10-3 3:11:10]