Java Spreadsheet

Im new to this group, mainly because I am taking a class that requires some Java. We are trying to make a Java spreadsheet, this teacher covers 2 chapters a week and for being a beginner it is way too fast for me. Has anyone had any experience in making a Java Spreadsheet that would like to give me a starting point? Im not a stranger to the language but I'm really at a loss at where to start. Any help would be appreciated, thanks!