001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.math3.ode.sampling;
019
020 /**
021 * This class is a step handler that does nothing.
022
023 * <p>This class is provided as a convenience for users who are only
024 * interested in the final state of an integration and not in the
025 * intermediate steps. Its handleStep method does nothing.</p>
026 *
027 * <p>Since this class has no internal state, it is implemented using
028 * the Singleton design pattern. This means that only one instance is
029 * ever created, which can be retrieved using the getInstance
030 * method. This explains why there is no public constructor.</p>
031 *
032 * @see StepHandler
033 * @version $Id: DummyStepHandler.java 1416643 2012-12-03 19:37:14Z tn $
034 * @since 1.2
035 */
036
037 public class DummyStepHandler implements StepHandler {
038
039 /** Private constructor.
040 * The constructor is private to prevent users from creating
041 * instances (Singleton design-pattern).
042 */
043 private DummyStepHandler() {
044 }
045
046 /** Get the only instance.
047 * @return the only instance
048 */
049 public static DummyStepHandler getInstance() {
050 return LazyHolder.INSTANCE;
051 }
052
053 /** {@inheritDoc} */
054 public void init(double t0, double[] y0, double t) {
055 }
056
057 /**
058 * Handle the last accepted step.
059 * This method does nothing in this class.
060 * @param interpolator interpolator for the last accepted step. For
061 * efficiency purposes, the various integrators reuse the same
062 * object on each call, so if the instance wants to keep it across
063 * all calls (for example to provide at the end of the integration a
064 * continuous model valid throughout the integration range), it
065 * should build a local copy using the clone method and store this
066 * copy.
067 * @param isLast true if the step is the last one
068 */
069 public void handleStep(final StepInterpolator interpolator, final boolean isLast) {
070 }
071
072 // CHECKSTYLE: stop HideUtilityClassConstructor
073 /** Holder for the instance.
074 * <p>We use here the Initialization On Demand Holder Idiom.</p>
075 */
076 private static class LazyHolder {
077 /** Cached field instance. */
078 private static final DummyStepHandler INSTANCE = new DummyStepHandler();
079 }
080 // CHECKSTYLE: resume HideUtilityClassConstructor
081
082 /** Handle deserialization of the singleton.
083 * @return the singleton instance
084 */
085 private Object readResolve() {
086 // return the singleton instance
087 return LazyHolder.INSTANCE;
088 }
089
090 }