code: protected Integer getFontSizeForZoom(double zoom) {
          double lower = -1;
          for (double upper : this.zoomToFontSizeMap.keySet()) {
              if (lower == -1) {
                  lower = upper;
                  if (zoom <= lower) return this.zoomToFontSizeMap.get(upper);
                  continue;
              }
              if (zoom > lower && zoom <= upper) {
                  return this.zoomToFontSizeMap.get(upper);
              }
              lower = upper;
          }
  
          return this.zoomToFontSizeMap.get(lower);
      }
docs: For a particular zoom, get the appropriate font size.
  
  @param zoom the zoom level
  @return an integer font size