There obviously is a class called Element. You can try going through the
API documentation, where "Element" appears five times, but I suspect, as Ernest is hinting, that it is either a class you have to write yourself, or a class your teacher is giving you.
You haven't provided enough information for us to help you properly, and I think you need to go back to whoever set the assignment and ask for more information about where to find these classes. Have you got a sheet of instructions for your project? Does it say anything about Element or what "h" is?