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CoordinateFilterΒΆ

The CoordinateFilter interface provides a useful handle for implementing your own querying and modifying operations. The interface defines a single method:

public void filter(Coordinate coord);

The following example shows a simple class to determine the bounds of a set of Geometry objects.:

class BoundsFilter implements CoordinateFilter {

  double minx,  miny,  maxx,  maxy;
  boolean first = true;

  /**
   * First coordinate visited initializes the min and max fields.
   * Subsequent coordinates are compared to current bounds.
   */
  public void filter(Coordinate c) {
      if (first) {
          minx = maxx = c.x;
          miny = maxy = c.y;
          first = false;
      } else {
          minx = Math.min(minx, c.x);
          miny = Math.min(miny, c.y);
          maxx = Math.max(maxx, c.x);
          maxy = Math.max(maxy, c.y);
      }
  }

  /**
   * Return bounds as a Rectangle2D object
   */
  Rectangle2D getBounds() {
      return new Rectangle2D.Double(minx, miny, maxx - minx, maxy - miny);
  }
}

And here is the filter being applied to a list of Geometry objects.:

List<Geometry> geoms = ...

BoundsFilter bf = new BoundsFilter();
for (Geometry g : geoms) {
    g.apply(bf);
}

Rectangle2D bounds = bf.getBounds();

The CoordinateFilter acts as a “visitor” allowing you to traverse all the coordinates in a Geometry.