public void mark(int readlimit){
  in.mark(readlimit);
  if (in.markSupported())   bytesLeftAtMark=bytesLeft;
}

public void mark ( int readlimit ) { in . mark ( readlimit ) ; if ( in . markSupported ( ) ) bytesLeftAtMark = bytesLeft ; }
mark the current position in the stream ( for future calls to reset ) . remember where we are within the proper content of the message , so that a reset method call can recreate our state properly .
