Thank you for the replies.
Here are the two culprits, I will make amendments to the naming of the panel class too thanks Winston.
When the button is clicked in the panel the information in the fields is used to create a new Person object, this is where I am presently stuck about how to get this object back over to the AddressBookGUI class and added to the AddressBook's list where I already have an existing addDetails method.
As mentioned above if I do this within the AddressBookGUI class just doing a
test run of it the object is added fine, I'm just having issues on getting the created object in the panel back across. I've tried creating a reference to the class in the panel but when I call the addDetails method I'm getting a nullpointerexception, which will be due to me not creating an instance of the class when I was trying to figure it out.
AddressBookGUI
EnterPersonDetailsPanel