code: private FieldPosition[] getPositivePrefixFieldPositions() {
          if (positivePrefixFieldPositions == null) {
              if (posPrefixPattern != null) {
                  positivePrefixFieldPositions = expandAffix(posPrefixPattern);
              } else {
                  positivePrefixFieldPositions = EmptyFieldPositionArray;
              }
          }
          return positivePrefixFieldPositions;
      }
docs: Returns the FieldPositions of the fields in the prefix used for
  positive numbers. This is not used if the user has explicitly set
  a positive prefix via <code>setPositivePrefix</code>. This is
  lazily created.
  
  @return FieldPositions in positive prefix