code: public boolean isCompetitor(Island isl) {
          for (Coordinate c : isl) {
              for (Coordinate d : islandCoordinates) {
                  if (c.sameColumn(d) || c.sameRow(d)) return true;
              }
          }
          return false;
      }
docs: Two islands are competitors if there is a horizontal or
  vertical line which goes through both islands