code: public void reset() throws IOException {
          synchronized (lock) {
              ensureOpen();
              if (markedChar < 0)
                  throw new IOException((markedChar == INVALIDATED)
                                        ? "Mark invalid"
                                        : "Stream not marked");
              nextChar = markedChar;
              skipLF = markedSkipLF;
          }
      }
docs: Resets the stream to the most recent mark.
  
  @exception  IOException  If the stream has never been marked,
  or if the mark has been invalidated