Java: Design the UI

In your promptAction method you ask for user input and in Java anything IO throws an exception, I believe. In the javadocs it says the readLine method can throw an exception "If an I/O error occurs". For more info on why it may throw an exception look at this stackoverflow post: https://stackoverflow.com/questions/2629649/java-what-are-ioexceptions-in-bufferedreaders-readline-for