A.BufferedOutputStreambis=newBufferedOutputStream(newFileOutputStream("c:\\demo.txt"),true);
B.BufferedOutputStreambis=newBufferedOutputStream(newFileOutputStream("c:\\demo.txt",true);
C.BufferedOutputStreambis=newBufferedOutputStream(newFileOutputStream("c:\\demo.txt",false));
D.BufferedOutputStreambis=newBufferedOutputStream(newFileOutputStream("c:\\demo.txt"),false);