# Interface BandedCoverage.Evaluator

All Superinterfaces:
  `Function<DirectPosition, double[]>`

All Known Subinterfaces:
  `GridCoverage​.Evaluator`

Enclosing class:
  `BandedCoverage`

public static interface BandedCoverage.Evaluator extends Function<DirectPosition, double[]>
Computes or interpolates values of sample dimensions at given positions. Values are computed by calls to `apply(DirectPosition)` and are returned as `double[]`.

## Multi-threading

Evaluators are not thread-safe. An instance of `Evaluator` should be created for each thread that need to compute sample values.

Since:
  1.1
See Also:
  - `BandedCoverage​.evaluator()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `double[]`
  `apply(DirectPosition point)`
  Returns a sequence of double values for a given point in the coverage.
  `BandedCoverage`
  `getCoverage()`
  Returns the coverage from which this evaluator is computing sample values.
  `boolean`
  `isNullIfOutside()`
  Returns whether to return `null` instead of throwing an exception if a point is outside coverage bounds.
  `boolean`
  `isWraparoundEnabled()`
  Returns `true` if this evaluator is allowed to wraparound coordinates that are outside the coverage.
  `void`
  `setNullIfOutside(boolean flag)`
  Sets whether to return `null` instead of throwing an exception if a point is outside coverage bounds.
  `void`
  `setWraparoundEnabled(boolean allow)`
  Specifies whether this evaluator is allowed to wraparound coordinates that are outside the coverage.

  ### Methods inherited from interface Function

  `andThen, compose`

- ## Method Details

  - ### getCoverage

    BandedCoverage getCoverage()
    Returns the coverage from which this evaluator is computing sample values. This is usually the instance on which the `BandedCoverage​.evaluator()` method has been invoked, but not necessarily. Evaluators are allowed to fetch values from a different source for better performances or accuracies.

    #### Example

    If the values of the enclosing coverage are interpolated from the values of another coverage, then this evaluator may use directly the values of the latter coverage. Doing so avoid to add more interpolations on values that are already interpolated.
    Returns:
      the source of sample values for this evaluator.

  - ### isNullIfOutside

    boolean isNullIfOutside()
    Returns whether to return `null` instead of throwing an exception if a point is outside coverage bounds. The default value is `false`, which means that the default `apply(DirectPosition)` behavior is to throw `PointOutsideCoverageException` for points outside bounds.
    Returns:
      whether `apply(DirectPosition)` return `null` for points outside coverage bounds.

  - ### setNullIfOutside

    void setNullIfOutside(boolean flag)
    Sets whether to return `null` instead of throwing an exception if a point is outside coverage bounds. The default value is `false`. Setting this flag to `true` may improve performances if the caller expects that many points will be outside coverage bounds, since it reduces the number of exceptions to be thrown.
    Parameters:
      `flag` - whether `apply(DirectPosition)` should use `null` return value instead of `PointOutsideCoverageException` for signaling that a point is outside coverage bounds.

  - ### isWraparoundEnabled

    boolean isWraparoundEnabled()
    Returns `true` if this evaluator is allowed to wraparound coordinates that are outside the coverage. The initial value is `false`. This method may continue to return `false` even after a call to `setWraparoundEnabled(true)` if no wraparound axis has been found in the coverage CRS, or if automatic wraparound is not supported.
    Returns:
      `true` if this evaluator may wraparound coordinates that are outside the coverage.
    Since:
      1.3

  - ### setWraparoundEnabled

    void setWraparoundEnabled(boolean allow)
    Specifies whether this evaluator is allowed to wraparound coordinates that are outside the coverage. If `true` and if a given coordinate is outside the coverage, then this evaluator may translate the point along a wraparound axis in an attempt to get the point inside the coverage. For example, if the coverage CRS has a longitude axis, then the evaluator may translate the longitude value by a multiple of 360°.
    Parameters:
      `allow` - whether to allow wraparound of coordinates that are outside the coverage.
    Since:
      1.3

  - ### apply

    double[] apply(DirectPosition point) throws CannotEvaluateException
    Returns a sequence of double values for a given point in the coverage. The CRS of the given point may be any coordinate reference system; coordinate conversions will be applied as needed. If the CRS of the point is undefined, then it is assumed to be the coverage CRS. The returned sequence includes a value for each sample dimension.
    Specified by:
      `apply` in interface `Function<DirectPosition, double[]>`
    Parameters:
      `point` - the position where to evaluate.
    Returns:
      the sample values at the specified point, or `null` if the point is outside the coverage. For performance reason, this method may return the same array on every method call by overwriting previous values. Callers should not assume that the array content stay valid for a long time.
    Throws:
      `PointOutsideCoverageException` - if the evaluation failed because the input point has invalid coordinates and the `isNullIfOutside()` flag is `false`.
      `CannotEvaluateException` - if the values cannot be computed at the specified coordinates for another reason. For example, this exception may be thrown if the coverage data type cannot be converted to `double` by an identity or widening conversion.