NullPointerException when added to a sheet

From the activation I call the method in the fragment:

fragmentContact = new FragmentContact(); fragmentContact.dataAdd(name, number, email); 

I add an object to the sheet with the method in the fragment and update the adapter:

 public void dataAdd(String name, String number, String email) { contactsList.add(new Contacts(name, number, email)); Collections.sort(contactsList, new Contacts.SortBeName()); mAdapter.dataChanged(contactsList); } 

Exception in this line:

 contactsList.add(new Contacts(name, number, email));