    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    }