code: public void doSubstitution(long number, StringBuilder toInsertInto, int position, int recursionCount) {
          // if this isn't a >>> substitution, just use the inherited version
          // of this function (which uses either a rule set or a DecimalFormat
          // to format its substitution value)
          if (ruleToUse == null) {
              super.doSubstitution(number, toInsertInto, position, recursionCount);
  
          } else {
              // a >>> substitution goes straight to a particular rule to
              // format the substitution value
              long numberToFormat = transformNumber(number);
              ruleToUse.doFormat(numberToFormat, toInsertInto, position + pos, recursionCount);
          }
      }
docs: If this is a &gt;&gt;&gt; substitution, use ruleToUse to fill in
  the substitution.  Otherwise, just use the superclass function.
  @param number The number being formatted
  @param toInsertInto The string to insert the result of this substitution
  into
  @param position The position of the rule text in toInsertInto