code: private void expandAffixes() {
          // Reuse one StringBuffer for better performance
          StringBuffer buffer = new StringBuffer();
          if (posPrefixPattern != null) {
              positivePrefix = expandAffix(posPrefixPattern, buffer);
              positivePrefixFieldPositions = null;
          }
          if (posSuffixPattern != null) {
              positiveSuffix = expandAffix(posSuffixPattern, buffer);
              positiveSuffixFieldPositions = null;
          }
          if (negPrefixPattern != null) {
              negativePrefix = expandAffix(negPrefixPattern, buffer);
              negativePrefixFieldPositions = null;
          }
          if (negSuffixPattern != null) {
              negativeSuffix = expandAffix(negSuffixPattern, buffer);
              negativeSuffixFieldPositions = null;
          }
      }
docs: Expand the affix pattern strings into the expanded affix strings.  If any
  affix pattern string is null, do not expand it.  This method should be
  called any time the symbols or the affix patterns change in order to keep
  the expanded affix strings up to date.