nio大文件分批传输

FileChannel文件传输效率高，利用了操作系统的零拷贝进行优化，传输文件大小上限是2g，可以分批传输

public static void main(String[] args) {
        try (
                FileChannel from = new FileInputStream("data.txt").getChannel();
                FileChannel to = new FileOutputStream("to.txt").getChannel();
        ) {
            long size = from.size();     
            for (long left = size; left > 0; ) {
                left -= from.transferTo((size - left), left, to);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }