code: public String normalize(CharSequence src) {
          if(src instanceof String) {
              // Fastpath: Do not construct a new String if the src is a String
              // and is already normalized.
              int spanLength=spanQuickCheckYes(src);
              if(spanLength==src.length()) {
                  return (String)src;
              }
              StringBuilder sb=new StringBuilder(src.length()).append(src, 0, spanLength);
              return normalizeSecondAndAppend(sb, src.subSequence(spanLength, src.length())).toString();
          }
          return normalize(src, new StringBuilder(src.length())).toString();
      }
docs: Returns the normalized form of the source string.
  @param src source string
  @return normalized src