NoClassdefFoundError

Hello All,
I am just starting to learn Java. I am trying to learn on my own using the book "Java Programming Fundamentals" by Kimberly Seefeld. I like the book so far but I have run into a problem. I have typed up the following example program from the book:
// A simple program solving an equation with a variable.
public class solveForX2 {
public static void main (String args[])
{
int x=0;//variable is initialized
System.out.println("If x+3=8, what is x?");
x=8-3; //an equation to solve for x
System.out.println("x = " + x);
}
}
I save it as solveForX2.java and javac compiles it into solveForX2.class, but when I try to run it I get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: solveForX2/class
I have checked it over multiple times and I cannot find any typos or mistakes on my part.
Can anyone tell me why this won't run?
Thanks,
Glen

Sounds like you are trying to run it with the command:
java solveForX2.class
The correct command is:
java solveForX2
".class" is the file extension for a class file. It is not part of the name of the class. If I had a dime for every time I've typed java something.java and received the same error.

That was it. Thanks a ton!
Glen