code: public void addIsland(Island isl) {
          if (LOG.isLoggable(Level.FINE)) {
              LOG.log(Level.FINE, "adding island: '{0}'", isl);
          }
          for (Coordinate coordinate : isl) {
              fixedRows.add(coordinate.row);
              fixedVertices.add(table.vertexAt(coordinate.row, coordinate.column));
          }
          fixedIslands.add(isl);
          islandMultimap.computeIfPresent(isl.size(), (s, i) -> {
              i.remove(isl);
              return (i.isEmpty() ? null : i);
          });
      }
docs: /*
  Commit an island in the match table
  Island will be part of the final alignment