code: public void buildIndex() {
      this.stringPosToRealPos = new HashMap<Integer, Integer>();
      int counter = 0;
      for (Integer idx : getAllIndices()) {
        this.stringPosToRealPos.put(counter, idx);
        counter++;
      }
    }
docs: This builds an index that aids in mapping of a SAX word to the real timeseries index.