Create a new class call it the name you want to call your exception. (i.e. MyNewException). This class must inherit from the Exception class.

Add a property to the class, which includes the error message for this new exception. You do not need to add a constructor, because you will get the no-argsconstructor from Java. You will want to have a way to display or output the error message. So I usually add a toString() method and/or a display() method.