code: public StringBuffer appendMessage(StringBuffer toAppendTo) {
          compare();
          if (messages.length()==0) {
              messages.append("[identical]");
          }
          // fix for JDK1.4 backwards incompatibility
          return toAppendTo.append(messages.toString());
      }
docs: Append the message from the result of this Diff instance to a specified
  StringBuffer
  @param toAppendTo
  @return specified StringBuffer with message appended