// Get the raster from a raster feature
public static Raster getRasterFromRasterFeature(Feature feature)
{
    // Check if the feature is a Raster feature
    if (feature.getGeometryType() == GeometryType.RASTER)   
    {
        // Get the RasterGeometry form the feature and return the Raster from it
        return feature.getGeometryAsRaster().getRaster();
    }

    // The Feature is not a Raster, so return nothing
    return null;
}