org.apache.commons.math3.ode.sampling

## Interface FixedStepHandler

-     public interface FixedStepHandler

  This interface represents a handler that should be called after each successful fixed step.

  This interface should be implemented by anyone who is interested in getting the solution of an ordinary differential equation at fixed time steps. Objects implementing this interface should be wrapped within an instance of `StepNormalizer` that itself is used as the general `StepHandler` by the integrator. The `StepNormalizer` object is called according to the integrator internal algorithms and it calls objects implementing this interface as necessary at fixed time steps.

  Since:
    1.2
  See Also:
    `StepHandler`, `StepNormalizer`

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `handleStep(double t, double[] y, double[] yDot, boolean isLast)` Handle the last accepted step
    `void` | `init(double t0, double[] y0, double t)` Initialize step handler at the start of an ODE integration.

- - ### Method Detail

    - #### init

          void init(double t0,
                  double[] y0,
                  double t)

      Initialize step handler at the start of an ODE integration.

      This method is called once at the start of the integration. It may be used by the step handler to initialize some internal data if needed.

      Parameters:
        `t0` - start value of the independent time variable
        `y0` - array containing the start value of the state vector
        `t` - target time for the integration

    - #### handleStep

          void handleStep(double t,
                        double[] y,
                        double[] yDot,
                        boolean isLast)

      Handle the last accepted step
      Parameters:
        `t` - time of the current step
        `y` - state vector at t. For efficiency purposes, the `StepNormalizer` class reuses the same array on each call, so if the instance wants to keep it across all calls (for example to provide at the end of the integration a complete array of all steps), it should build a local copy store this copy.
        `yDot` - derivatives of the state vector state vector at t. For efficiency purposes, the `StepNormalizer` class reuses the same array on each call, so if the instance wants to keep it across all calls (for example to provide at the end of the integration a complete array of all steps), it should build a local copy store this copy.
        `isLast` - true if the step is the last one

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