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Java example source code file (ReappearingEventTest.java)

This example Java source code file (ReappearingEventTest.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.

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Java - Java tags/keywords

action, dimensionmismatchexception, dormandprince853integrator, event, firstorderdifferentialequations, firstorderintegrator, graggbulirschstoerintegrator, maxcountexceededexception, nobracketingexception, numberistoosmallexception, ode, pegasussolver, reappearingeventtest, test, util

The ReappearingEventTest.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.events;

import org.junit.Assert;

import java.util.Arrays;

import org.apache.commons.math3.analysis.solvers.PegasusSolver;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.exception.NoBracketingException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.ode.FirstOrderDifferentialEquations;
import org.apache.commons.math3.ode.FirstOrderIntegrator;
import org.apache.commons.math3.ode.events.EventHandler;
import org.apache.commons.math3.ode.nonstiff.DormandPrince853Integrator;
import org.apache.commons.math3.ode.nonstiff.GraggBulirschStoerIntegrator;
import org.junit.Test;

public class ReappearingEventTest {
    @Test
    public void testDormandPrince()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        double tEnd = test(1);
        Assert.assertEquals(10.0, tEnd, 1e-7);
    }

    @Test
    public void testGragg()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        double tEnd = test(2);
        Assert.assertEquals(10.0, tEnd, 1e-7);
    }

    public double test(int integratorType)
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        double e = 1e-15;
        FirstOrderIntegrator integrator;
        integrator = (integratorType == 1)
                     ? new DormandPrince853Integrator(e, 100.0, 1e-7, 1e-7)
                     : new GraggBulirschStoerIntegrator(e, 100.0, 1e-7, 1e-7);
        PegasusSolver rootSolver = new PegasusSolver(e, e);
        integrator.addEventHandler(new Event(), 0.1, e, 1000, rootSolver);
        double t0 = 6.0;
        double tEnd = 10.0;
        double[] y = {2.0, 2.0, 2.0, 4.0, 2.0, 7.0, 15.0};
        return integrator.integrate(new Ode(), t0, y, tEnd, y);
    }

    private static class Ode implements FirstOrderDifferentialEquations {
        public int getDimension() {
            return 7;
        }

        public void computeDerivatives(double t, double[] y, double[] yDot) {
            Arrays.fill(yDot, 1.0);
        }
    }

    /** State events for this unit test. */
    protected static class Event implements EventHandler {

        public void init(double t0, double[] y0, double t) {
        }

        public double g(double t, double[] y) {
            return y[6] - 15.0;
        }

        public Action eventOccurred(double t, double[] y, boolean increasing) {
            return Action.STOP;
        }

        public void resetState(double t, double[] y) {
            // Never called.
        }
    }
}

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