"jhonny", you have previously been warned on one or more occasions regarding adjusting your display name to meet JavaRanch standards. This is not optional. Please take a look at the JavaRanch Naming Policy and adjust your display name to match it prior to your next post.
Your display name must be a first and a last name separated by a space character, and must not be obviously fictitious.
Be aware that accounts with invalid display names are disabled.
In general if classpath has been setup correctly the error should not occur. However, make sure that your classpath includes .; i.e. path to your current folder where the program is located. If not, the above error will show up and this may be all you need to fix your problem.