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.math.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 $Revision: 811827 $ $Date: 2009-09-06 17:32:50 +0200 (dim. 06 sept. 2009) $
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 /** Determines whether this handler needs dense output.
054 * Since this handler does nothing, it does not require dense output.
055 * @return always false
056 */
057 public boolean requiresDenseOutput() {
058 return false;
059 }
060
061 /** Reset the step handler.
062 * Initialize the internal data as required before the first step is
063 * handled.
064 */
065 public void reset() {
066 }
067
068 /**
069 * Handle the last accepted step.
070 * This method does nothing in this class.
071 * @param interpolator interpolator for the last accepted step. For
072 * efficiency purposes, the various integrators reuse the same
073 * object on each call, so if the instance wants to keep it across
074 * all calls (for example to provide at the end of the integration a
075 * continuous model valid throughout the integration range), it
076 * should build a local copy using the clone method and store this
077 * copy.
078 * @param isLast true if the step is the last one
079 */
080 public void handleStep(final StepInterpolator interpolator, final boolean isLast) {
081 }
082
083 // CHECKSTYLE: stop HideUtilityClassConstructor
084 /** Holder for the instance.
085 * <p>We use here the Initialization On Demand Holder Idiom.</p>
086 */
087 private static class LazyHolder {
088 /** Cached field instance. */
089 private static final DummyStepHandler INSTANCE = new DummyStepHandler();
090 }
091 // CHECKSTYLE: resume HideUtilityClassConstructor
092
093 /** Handle deserialization of the singleton.
094 * @return the singleton instance
095 */
096 private Object readResolve() {
097 // return the singleton instance
098 return LazyHolder.INSTANCE;
099 }
100
101 }