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1   /* This file is part of COPAL (COntext Provisioning for All).
2    *
3    * COPAL is a part of SM4All (Smart hoMes for All) project.
4    *
5    * COPAL is free software: you can redistribute it and/or modify
6    * it under the terms of the GNU Lesser General Public License as published by
7    * the Free Software Foundation, either version 3 of the License, or
8    * (at your option) any later version.
9    *
10   * COPAL is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   * GNU Lesser General Public License for more details.
14   *
15   * You should have received a copy of the GNU Lesser General Public License
16   * along with COPAL. If not, see <http://www.gnu.org/licenses/>.
17   */
18  package at.ac.tuwien.infosys.sm4all.copal.api.util;
19  
20  /**
21   * The interface which represents an object that can be observed.
22   * 
23   * @param <E> the type of change represented as an {@link Enum}.
24   * @param <T> the type of changed object.
25   * @param <O> the type of {@link Observer} that can attach and detach to this
26   *        {@link Observable}.
27   * @author sanjin
28   */
29  public interface Observable<E extends Enum<?>, T, O extends Observer<E, T>> {
30  
31      /**
32       * Attaches specified {@link Observer} so it will in future receive
33       * notifications on changes.
34       * 
35       * @param observer the {@link Observer}.
36       */
37      void attach(O observer);
38  
39      /**
40       * Detach specified {@link Observer} so it will not receive any future
41       * notifications on changes.
42       * 
43       * @param observer the {@link Observer}.
44       */
45      void detach(O observer);
46  }