Welcome to the forum. UseCodeTags to post code so that it is readable. And to get better help sooner, always post a SSCCE. Your question is about a class that's not found. JMenus and ActionListeners and the like have nothing to do with your question and are just so much clutter when it comes to reading the code.
Dialog.ModalityType. Or import static ...Dialog.*; and you will be able to use the unqualified name in your code.
There are no new questions, but there may be new answers.