code: private static final String getString(CharacterIterator text, int start, int length) {
          StringBuilder result = new StringBuilder(length);
          int offset = text.getIndex();
          text.setIndex(start);
          for (int i = 0; i < length; i++) {
              result.append(text.current());
              text.next();
          }
          text.setIndex(offset);
          return result.toString();
      }
docs: Gets a substring out of a CharacterIterator
  
  Java porting note: Not available in ICU4C
  
  @param text CharacterIterator
  @param start start offset
  @param length of substring
  @return substring from text starting at start and length length