public class User implements Observable {
    private PropertyChangeRegistry registry = new PropertyChangeRegistry();

   private String firstName;
   private String lastName;

   @Bindable
   public String getFirstName() {
       return this.firstName;
   }

   @Bindable
   public String getLastName() {
       return this.lastName;
   }

   public void setFirstName(String firstName) {
       this.firstName = firstName;
       registry.notifyChange(this, BR.firstName);

   }

   public void setLastName(String lastName) {
       this.lastName = lastName;
       registry.notifyChange(this, BR.lastName);
   }


    @Override
    public void addOnPropertyChangedCallback(OnPropertyChangedCallback callback) {
        registry.add(callback);
    }

    @Override
    public void removeOnPropertyChangedCallback(OnPropertyChangedCallback callback) {
        registry.remove(callback);
    }
}