1   /* Copyright 2002-2026 CS GROUP
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS 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  package org.orekit.utils.drivers;
18  
19  import org.orekit.time.AbsoluteDate;
20  
21  /** Interface for observing parameters changes.
22   * @see ParameterDriver
23   * @author Luc Maisonobe
24   * @since 8.0
25   */
26  public interface ParameterObserver extends BaseParameterObserver<ParameterDriver, ParameterObserver> {
27  
28      /** Notify that a parameter reference date has been changed.
29       * <p>
30       * The default implementation does nothing
31       * </p>
32       * @param previousReferenceDate previous date (null if it is the first time
33       * the reference date is changed)
34       * @param driver parameter driver that has been changed
35       * @since 9.0
36       */
37      default void referenceDateChanged(final AbsoluteDate previousReferenceDate, final ParameterDriver driver) {
38          // nothing by default
39      }
40  
41      /** Notify that a parameter reference value has been changed.
42       * <p>
43       * The default implementation does nothing
44       * </p>
45       * @param previousReferenceValue previous reference value
46       * @param driver parameter driver that has been changed
47       * @since 9.0
48       */
49      default void referenceValueChanged(final double previousReferenceValue, final ParameterDriver driver) {
50          // nothing by default
51      }
52  
53      /** Notify that a parameter value has been changed.
54       * @param previousValue previous value
55       * @param driver        parameter driver that has been changed
56       */
57      void valueChanged(double previousValue, ParameterDriver driver);
58  
59  }