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 org.apache.commons.math.ode.sampling; 19 20 /** 21 * This class is a step handler that does nothing. 22 23 * <p>This class is provided as a convenience for users who are only 24 * interested in the final state of an integration and not in the 25 * intermediate steps. Its handleStep method does nothing.</p> 26 * 27 * <p>Since this class has no internal state, it is implemented using 28 * the Singleton design pattern. This means that only one instance is 29 * ever created, which can be retrieved using the getInstance 30 * method. This explains why there is no public constructor.</p> 31 * 32 * @see StepHandler 33 * @version $Revision: 811827 $ $Date: 2009-09-06 17:32:50 +0200 (dim. 06 sept. 2009) $ 34 * @since 1.2 35 */ 36 37 public class DummyStepHandler implements StepHandler { 38 39 /** Private constructor. 40 * The constructor is private to prevent users from creating 41 * instances (Singleton design-pattern). 42 */ 43 private DummyStepHandler() { 44 } 45 46 /** Get the only instance. 47 * @return the only instance 48 */ 49 public static DummyStepHandler getInstance() { 50 return LazyHolder.INSTANCE; 51 } 52 53 /** Determines whether this handler needs dense output. 54 * Since this handler does nothing, it does not require dense output. 55 * @return always false 56 */ 57 public boolean requiresDenseOutput() { 58 return false; 59 } 60 61 /** Reset the step handler. 62 * Initialize the internal data as required before the first step is 63 * handled. 64 */ 65 public void reset() { 66 } 67 68 /** 69 * Handle the last accepted step. 70 * This method does nothing in this class. 71 * @param interpolator interpolator for the last accepted step. For 72 * efficiency purposes, the various integrators reuse the same 73 * object on each call, so if the instance wants to keep it across 74 * all calls (for example to provide at the end of the integration a 75 * continuous model valid throughout the integration range), it 76 * should build a local copy using the clone method and store this 77 * copy. 78 * @param isLast true if the step is the last one 79 */ 80 public void handleStep(final StepInterpolator interpolator, final boolean isLast) { 81 } 82 83 // CHECKSTYLE: stop HideUtilityClassConstructor 84 /** Holder for the instance. 85 * <p>We use here the Initialization On Demand Holder Idiom.</p> 86 */ 87 private static class LazyHolder { 88 /** Cached field instance. */ 89 private static final DummyStepHandler INSTANCE = new DummyStepHandler(); 90 } 91 // CHECKSTYLE: resume HideUtilityClassConstructor 92 93 /** Handle deserialization of the singleton. 94 * @return the singleton instance 95 */ 96 private Object readResolve() { 97 // return the singleton instance 98 return LazyHolder.INSTANCE; 99 } 100 101 } 102
