1 /*
2  *  Licensed to the Apache Software Foundation (ASF) under one or more
3  *  contributor license agreements.  See the NOTICE file distributed with
4  *  this work for additional information regarding copyright ownership.
5  *  The ASF licenses this file to You under the Apache License, Version 2.0
6  *  (the "License"); you may not use this file except in compliance with
7  *  the License.  You may obtain a copy of the License at
8  *
9  *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  *  Unless required by applicable law or agreed to in writing, software
12  *  distributed under the License is distributed on an "AS IS" BASIS,
13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *  See the License for the specific language governing permissions and
15  *  limitations under the License.
16  */
17 
18 package java.util;
19 
20 
21 /**
22  * {@code Observer} is the interface to be implemented by objects that
23  * receive notification of updates on an {@code Observable} object.
24  *
25  * @see Observable
26  */
27 public interface Observer {
28 
29     /**
30      * This method is called if the specified {@code Observable} object's
31      * {@code notifyObservers} method is called (because the {@code Observable}
32      * object has been updated.
33      *
34      * @param observable
35      *            the {@link Observable} object.
36      * @param data
37      *            the data passed to {@link Observable#notifyObservers(Object)}.
38      */
update(Observable observable, Object data)39     void update(Observable observable, Object data);
40 }
41