private void fillInStaffOnProjectList(int projectID){
        listOfUsers.clear();
        if (projectID >=1)
        {
            try{
                ResultSet staffOnProjectResultSet = null;
                Statement staff;
                staff = connection.createStatement();
                staffOnProjectResultSet = staff.executeQuery("SELECT Project.projectID, User.userID, User.firstName, User.surname, Staff.role FROM User INNER JOIN (Staff INNER JOIN (Project INNER JOIN StaffOnProjects ON Project.projectID = StaffOnProjects.projectID) ON Staff.staffID = StaffOnProjects.staffID) ON User.userID = Staff.staffID WHERE Project.projectID=" + projectID + ";"); 
                int userID;
                String firstName;
                String surname;
                String role;

                while(staffOnProjectResultSet.next())
                {
                    userID = staffOnProjectResultSet.getInt("userID");
                    firstName = staffOnProjectResultSet.getString("firstName");
                    surname = staffOnProjectResultSet.getString("surname");
                    role = staffOnProjectResultSet.getString("role");
                    User user= new User(userID,firstName,surname, "","");
                    listOfUsers.add(user);
                    listStaffOnProject.setListData(listOfUsers);
                    UserListCellRenderer renderer = new UserListCellRenderer();  //custom cell renderer to display property rather than useless object.toString()
                    listStaffOnProject.setCellRenderer(renderer);
                }
            }catch(SQLException err)
                    {
                        System.out.println("ERROR: " + err);
                            JOptionPane.showMessageDialog(null,"* Cannot connect to database! *");
                            System.exit(1);
                    }
        }
        else{
            listOfUsers.clear();
            listStaffOnProject.setListData(listOfUsers);
            listStaffOnProject.repaint();
        }
    }