code: private static String getDeliveryReceiptValue(String attrName, String source)
              throws IndexOutOfBoundsException {
          String tmpAttr = attrName + ":";
          int startIndex = source.indexOf(tmpAttr);
          if (startIndex < 0) {
              return null;
          }
          startIndex = startIndex + tmpAttr.length();
          int endIndex = source.indexOf(" ", startIndex);
          if (endIndex > 0) {
              return source.substring(startIndex, endIndex);
          }
          return source.substring(startIndex);
      }
docs: Get the delivery receipt attribute value.
  
  @param attrName is the attribute name.
  @param source the original source id:IIIIIIIIII sub:SSS dlvrd:DDD submit
  date:YYMMDDhhmm done date:YYMMDDhhmm stat:DDDDDDD err:E
  Text:....................
  @return the value of specified attribute.
  @throws IndexOutOfBoundsException