## org.apache.commons.math.ode
Interface FirstOrderIntegrator

All Superinterfaces:
  ODEIntegrator

All Known Implementing Classes:
  AbstractIntegrator, AdamsBashforthIntegrator, AdamsIntegrator, AdamsMoultonIntegrator, AdaptiveStepsizeIntegrator, ClassicalRungeKuttaIntegrator, DormandPrince54Integrator, DormandPrince853Integrator, EmbeddedRungeKuttaIntegrator, EulerIntegrator, GillIntegrator, GraggBulirschStoerIntegrator, HighamHall54Integrator, MidpointIntegrator, MultistepIntegrator, RungeKuttaIntegrator, ThreeEighthesIntegrator

    public interface FirstOrderIntegrator

extends ODEIntegrator

This interface represents a first order integrator for differential equations.

The classes which are devoted to solve first order differential equations should implement this interface. The problems which can be handled should implement the `FirstOrderDifferentialEquations` interface.

Since:
  1.2
Version:
  $Revision: 811786 $ $Date: 2009-09-06 05:36:08 -0400 (Sun, 06 Sep 2009) $
See Also:
  `FirstOrderDifferentialEquations`, `StepHandler`, `EventHandler`

Method Summary
`double` `integrate(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y)` Integrate the differential equations up to the given time.

Methods inherited from interface org.apache.commons.math.ode.ODEIntegrator
`addEventHandler, addStepHandler, clearEventHandlers, clearStepHandlers, getCurrentSignedStepsize, getCurrentStepStart, getEvaluations, getEventHandlers, getMaxEvaluations, getName, getStepHandlers, setMaxEvaluations`

Method Detail

### integrate

    double integrate(FirstOrderDifferentialEquations equations,
                     double t0,
                     double[] y0,
                     double t,
                     double[] y)
                     throws DerivativeException,
                            IntegratorException

  Integrate the differential equations up to the given time.

  This method solves an Initial Value Problem (IVP).

  Since this method stores some internal state variables made available in its public interface during integration (`ODEIntegrator.getCurrentSignedStepsize()`), it is not thread-safe.

  Parameters:
    `equations` - differential equations to integrate
    `t0` - initial time
    `y0` - initial value of the state vector at t0
    `t` - target time for the integration (can be set to a value smaller than `t0` for backward integration)
    `y` - placeholder where to put the state vector at each successful step (and hence at the end of integration), can be the same object as y0
  Returns:
    stop time, will be the same as target time if integration reached its target, but may be different if some `EventHandler` stops it at some point.
  Throws:
    `IntegratorException` - if the integrator cannot perform integration
    `DerivativeException` - this exception is propagated to the caller if the underlying user function triggers one

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