## The Commons Math *SecondOrderDifferentialEquations.java* 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.math.ode;
/** This interface represents a second order differential equations set.
* <p>This interface should be implemented by all real second order
* differential equation problems before they can be handled by the
* integrators {@link SecondOrderIntegrator#integrate} method.</p>
*
* <p>A second order differential equations problem, as seen by an
* integrator is the second time derivative <code>d2Y/dt^2 of a
* state vector <code>Y, both being one dimensional
* arrays. From the integrator point of view, this derivative depends
* only on the current time <code>t, on the state vector
* <code>Y and on the first time derivative of the state
* vector.</p>
*
* <p>For real problems, the derivative depends also on parameters
* that do not belong to the state vector (dynamical model constants
* for example). These constants are completely outside of the scope
* of this interface, the classes that implement it are allowed to
* handle them as they want.</p>
*
* @see SecondOrderIntegrator
* @see FirstOrderConverter
* @see FirstOrderDifferentialEquations
* @version $Revision: 811786 $ $Date: 2009-09-06 05:36:08 -0400 (Sun, 06 Sep 2009) $
* @since 1.2
*/
public interface SecondOrderDifferentialEquations {
/** Get the dimension of the problem.
* @return dimension of the problem
*/
int getDimension();
/** Get the current time derivative of the state vector.
* @param t current value of the independent <I>time variable
* @param y array containing the current value of the state vector
* @param yDot array containing the current value of the first derivative
* of the state vector
* @param yDDot placeholder array where to put the second time derivative
* of the state vector
* @throws DerivativeException this exception is propagated to the caller if the
* underlying user function triggers one
*/
void computeSecondDerivatives(double t, double[] y, double[] yDot,
double[] yDDot) throws DerivativeException;
}

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