Android Java快速给File追加头信息

     try {
           String header="GexYY";
           RandomAccessFile  src = new RandomAccessFile(mFile, "rw");
            int srcLength = (int) src.length();
            byte[] buff = new byte[srcLength];
            byte[] header = header.getBytes();
            src.read(buff, 0, srcLength);
            src.seek(0);
            src.write(header);
            src.seek(header.length);
            src.write(buff);
            src.close();
        } catch (Exception e) {
            e.printStackTrace();
        }