code: public static long copy(FileInputStream in, FileOutputStream out) throws IORuntimeException {
  		Assert.notNull(in, "FileInputStream is null!");
  		Assert.notNull(out, "FileOutputStream is null!");
  
  		final FileChannel inChannel = in.getChannel();
  		final FileChannel outChannel = out.getChannel();
  
  		try {
  			return inChannel.transferTo(0, inChannel.size(), outChannel);
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}
docs: 拷贝文件流，使用NIO
  
  @param in 输入
  @param out 输出
  @return 拷贝的字节数
  @throws IORuntimeException IO异常