java的流复制问题

try {

fis=new FileInputStream("E:/3.mp3");

//输出流

fos=new FileOutputStream("D:/3.mp3");

//字节缓冲区

byte[] buffer=new byte[1024];

int len=0;

while((len=fis.read(buffer))!=-1){
fos.write(buffer, 0, len);

fos.flush();

}

} catch (Exception e) {
e.printStackTrace();

} finally{
fos.close();

fis.close();


}