code: public double distance(final Coordinate c) {
          final double dx = getX() - c.getX();
          final double dy = getY() - c.getY();
          return Math.sqrt(dx * dx + dy * dy);
      }
docs: Computes the 2-dimensional Euclidean distance to another location. The Z-ordinate is ignored.
  
  @param c
  a point
  @return the 2-dimensional Euclidean distance between the locations