public class UserDAOImplFile implements UserDAO { @Override public boolean insert(User user) { ObjectOutputStream out = null; try { ArrayList userList = selectUserList(); userList.add(user); out = new ObjectOutputStream(new FileOutputStream("user.dat")); out.writeObject(userList); } catch (IOException e) { e.printStackTrace(); } finally { try { if (out != null) out.close(); } catch (IOException ..