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Java example source code file (DummyStepInterpolator.java)

This example Java source code file (DummyStepInterpolator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractstepinterpolator, classnotfoundexception, dummystepinterpolator, equationsmapper, ioexception, objectinput, objectoutput, override

The DummyStepInterpolator.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math3.ode.sampling;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import org.apache.commons.math3.ode.EquationsMapper;

/** This class is a step interpolator that does nothing.
 *
 * <p>This class is used when the {@link StepHandler "step handler"}
 * set up by the user does not need step interpolation. It does not
 * recompute the state when {@link AbstractStepInterpolator#setInterpolatedTime
 * setInterpolatedTime} is called. This implies the interpolated state
 * is always the state at the end of the current step.</p>
 *
 * @see StepHandler
 *
 * @since 1.2
 */

public class DummyStepInterpolator
  extends AbstractStepInterpolator {

  /** Serializable version identifier. */
  private static final long serialVersionUID = 1708010296707839488L;

  /** Current derivative. */
  private double[] currentDerivative;

  /** Simple constructor.
   * This constructor builds an instance that is not usable yet, the
   * <code>AbstractStepInterpolator.reinitialize protected method
   * should be called before using the instance in order to initialize
   * the internal arrays. This constructor is used only in order to delay
   * the initialization in some cases. As an example, the {@link
   * org.apache.commons.math3.ode.nonstiff.EmbeddedRungeKuttaIntegrator} uses
   * the prototyping design pattern to create the step interpolators by
   * cloning an uninitialized model and latter initializing the copy.
   */
  public DummyStepInterpolator() {
    super();
    currentDerivative = null;
  }

  /** Simple constructor.
   * @param y reference to the integrator array holding the state at
   * the end of the step
   * @param yDot reference to the integrator array holding the state
   * derivative at some arbitrary point within the step
   * @param forward integration direction indicator
   */
  public DummyStepInterpolator(final double[] y, final double[] yDot, final boolean forward) {
    super(y, forward, new EquationsMapper(0, y.length), new EquationsMapper[0]);
    currentDerivative = yDot;
  }

  /** Copy constructor.
   * @param interpolator interpolator to copy from. The copy is a deep
   * copy: its arrays are separated from the original arrays of the
   * instance
   */
  public DummyStepInterpolator(final DummyStepInterpolator interpolator) {
    super(interpolator);
    if (interpolator.currentDerivative != null) {
        currentDerivative = interpolator.currentDerivative.clone();
    }
  }

  /** Really copy the finalized instance.
   * @return a copy of the finalized instance
   */
  @Override
  protected StepInterpolator doCopy() {
    return new DummyStepInterpolator(this);
  }

  /** Compute the state at the interpolated time.
   * In this class, this method does nothing: the interpolated state
   * is always the state at the end of the current step.
   * @param theta normalized interpolation abscissa within the step
   * (theta is zero at the previous time step and one at the current time step)
   * @param oneMinusThetaH time gap between the interpolated time and
   * the current time
   */
  @Override
  protected void computeInterpolatedStateAndDerivatives(final double theta, final double oneMinusThetaH) {
      System.arraycopy(currentState,      0, interpolatedState,       0, currentState.length);
      System.arraycopy(currentDerivative, 0, interpolatedDerivatives, 0, currentDerivative.length);
  }

  /** Write the instance to an output channel.
   * @param out output channel
   * @exception IOException if the instance cannot be written
   */
  @Override
  public void writeExternal(final ObjectOutput out)
    throws IOException {

      // save the state of the base class
    writeBaseExternal(out);

    if (currentDerivative != null) {
        for (int i = 0; i < currentDerivative.length; ++i) {
            out.writeDouble(currentDerivative[i]);
        }
    }

  }

  /** Read the instance from an input channel.
   * @param in input channel
   * @exception IOException if the instance cannot be read
   */
  @Override
  public void readExternal(final ObjectInput in)
    throws IOException, ClassNotFoundException {

    // read the base class
    final double t = readBaseExternal(in);

    if (currentState == null) {
        currentDerivative = null;
    } else {
        currentDerivative  = new double[currentState.length];
        for (int i = 0; i < currentDerivative.length; ++i) {
            currentDerivative[i] = in.readDouble();
        }
    }

    // we can now set the interpolated time and state
    setInterpolatedTime(t);

  }

}

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