复制一个视频, 提示用户百分比完成度

public static void copyVideo() throws Exception{
		File file = new File("d:\\test.mp4");
		FileInputStream fis = new FileInputStream(file);
		
		FileOutputStream fos = new FileOutputStream("d:\\test-副本.mp4");
		long length = file.length();
		long count = 0;
		long lastbfb = 0;
		int len;
		byte[] bs = new byte[8192];
		while((len=fis.read(bs))!=-1) {
			fos.write(bs,0,len);
			count +=len;
			long bf = (count*100)/length;
			if(bf>lastbfb){
				System.out.println(bf+"%");
				lastbfb = bf;
			}
		}
		fis.close();
		fos.close();
	}