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Java example source code file (TestProblem1.java)

This example Java source code file (TestProblem1.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

override, testproblem1, testproblemabstract

The TestProblem1.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;

import org.apache.commons.math3.util.FastMath;

/**
 * This class is used in the junit tests for the ODE integrators.

 * <p>This specific problem is the following differential equation :
 * <pre>
 *    y' = -y
 * </pre>
 * the solution of this equation is a simple exponential function :
 * <pre>
 *   y (t) = y (t0) exp (t0-t)
 * </pre>
 * </p>

 */
public class TestProblem1
  extends TestProblemAbstract {

  /** theoretical state */
  private double[] y;

  /**
   * Simple constructor.
   */
  public TestProblem1() {
    super();
    double[] y0 = { 1.0, 0.1 };
    setInitialConditions(0.0, y0);
    setFinalConditions(4.0);
    double[] errorScale = { 1.0, 1.0 };
    setErrorScale(errorScale);
    y = new double[y0.length];
  }

  @Override
  public void doComputeDerivatives(double t, double[] y, double[] yDot) {

    // compute the derivatives
    for (int i = 0; i < getDimension(); ++i)
      yDot[i] = -y[i];

  }

  @Override
  public double[] computeTheoreticalState(double t) {
    double c = FastMath.exp (getInitialTime() - t);
    for (int i = 0; i < getDimension(); ++i) {
      y[i] = c * getInitialState()[i];
    }
    return y;
  }

}

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