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.math4.legacy.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 * @since 1.2 34 */ 35 36 public final class DummyStepHandler implements StepHandler { 37 38 /** Private constructor. 39 * The constructor is private to prevent users from creating 40 * instances (Singleton design-pattern). 41 */ 42 private DummyStepHandler() { 43 } 44 45 /** Get the only instance. 46 * @return the only instance 47 */ 48 public static DummyStepHandler getInstance() { 49 return LazyHolder.INSTANCE; 50 } 51 52 /** {@inheritDoc} */ 53 @Override 54 public void init(double t0, double[] y0, double t) { 55 } 56 57 /** 58 * Handle the last accepted step. 59 * This method does nothing in this class. 60 * @param interpolator interpolator for the last accepted step. For 61 * efficiency purposes, the various integrators reuse the same 62 * object on each call, so if the instance wants to keep it across 63 * all calls (for example to provide at the end of the integration a 64 * continuous model valid throughout the integration range), it 65 * should build a local copy using the clone method and store this 66 * copy. 67 * @param isLast true if the step is the last one 68 */ 69 @Override 70 public void handleStep(final StepInterpolator interpolator, final boolean isLast) { 71 } 72 73 // CHECKSTYLE: stop HideUtilityClassConstructor 74 /** Holder for the instance. 75 * <p>We use here the Initialization On Demand Holder Idiom.</p> 76 */ 77 private static final class LazyHolder { 78 /** Cached field instance. */ 79 private static final DummyStepHandler INSTANCE = new DummyStepHandler(); 80 } 81 // CHECKSTYLE: resume HideUtilityClassConstructor 82 83 /** Handle deserialization of the singleton. 84 * @return the singleton instance 85 */ 86 private Object readResolve() { 87 // return the singleton instance 88 return LazyHolder.INSTANCE; 89 } 90 }