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 018package 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 * @since 1.2 034 */ 035 036public class DummyStepHandler implements StepHandler { 037 038 /** Private constructor. 039 * The constructor is private to prevent users from creating 040 * instances (Singleton design-pattern). 041 */ 042 private DummyStepHandler() { 043 } 044 045 /** Get the only instance. 046 * @return the only instance 047 */ 048 public static DummyStepHandler getInstance() { 049 return LazyHolder.INSTANCE; 050 } 051 052 /** {@inheritDoc} */ 053 public void init(double t0, double[] y0, double t) { 054 } 055 056 /** 057 * Handle the last accepted step. 058 * This method does nothing in this class. 059 * @param interpolator interpolator for the last accepted step. For 060 * efficiency purposes, the various integrators reuse the same 061 * object on each call, so if the instance wants to keep it across 062 * all calls (for example to provide at the end of the integration a 063 * continuous model valid throughout the integration range), it 064 * should build a local copy using the clone method and store this 065 * copy. 066 * @param isLast true if the step is the last one 067 */ 068 public void handleStep(final StepInterpolator interpolator, final boolean isLast) { 069 } 070 071 // CHECKSTYLE: stop HideUtilityClassConstructor 072 /** Holder for the instance. 073 * <p>We use here the Initialization On Demand Holder Idiom.</p> 074 */ 075 private static class LazyHolder { 076 /** Cached field instance. */ 077 private static final DummyStepHandler INSTANCE = new DummyStepHandler(); 078 } 079 // CHECKSTYLE: resume HideUtilityClassConstructor 080 081 /** Handle deserialization of the singleton. 082 * @return the singleton instance 083 */ 084 private Object readResolve() { 085 // return the singleton instance 086 return LazyHolder.INSTANCE; 087 } 088 089}