code: protected boolean addTerm() {
          final boolean termAdded = !tokens.isEmpty();
          if (termAdded) {
              final String term = tokens.pop();
              clearAttributes();
              termAtt.append(term);
          }
          return termAdded;
      }
docs: Adds a term, if one exists, from the tokens collection.
  
  @return whether or not a new term was added