Thread: run.bat error

Code:

Exception in thread "main" java.lang.NoClassDefFoundError: Gui
Caused by: java.lang.ClassNotFoundException: Gui
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: Gui.  Program will exit.
Press any key to continue . . .

I have been looking and trying to fix this problem for awhile now. Figured someone here maybe be able to help. Thanks.