code: public static boolean isToken (@Nullable final String sToken)
    {
      // Check length
      if (StringHelper.hasNoText (sToken))
        return false;
  
      // Check that all chars are token chars
      final char [] aChars = sToken.toCharArray ();
      for (final char c : aChars)
        if (!isTokenChar (c))
          return false;
      return true;
    }
docs: Check if the passed string is a valid MIME token by checking that the
  length is at least 1 and all chars match the {@link #isTokenChar(char)}
  condition.
  
  @param sToken
  The token to be checked. May be <code>null</code>.
  @return <code>true</code> if the passed string is valid token,
  <code>false</code> otherwise.