public static String getCharset(File file) {
        String charset = "GBK";
        byte[] first3Bytes = new byte[3];
        try {
            boolean checked = false;
            BufferedInputStream bis = new BufferedInputStream(
                  new FileInputStream(file));
            bis.mark(0);
            int read = bis.read(first3Bytes, 0, 3);
            if (read == -1)
                return charset;
            if (first3Bytes[0] == (byte) 0xFF && first3Bytes[1] == (byte) 0xFE) {
                charset = "utf-8LE";
                checked = true;
            } else if (first3Bytes[0] == (byte) 0xFE && first3Bytes[1]
                == (byte) 0xFF) {
                charset = "utf-8BE";
                checked = true;
            } else if (first3Bytes[0] == (byte) 0xEF && first3Bytes[1]
                    == (byte) 0xBB
                    && first3Bytes[2] == (byte) 0xBF) {
                charset = "UTF-8";
                checked = true;
            }
            bis.reset();
            if (!checked) {
                int loc = 0;
                while ((read = bis.read()) != -1) {
                    loc++;
                    if (read >= 0xF0)
                        break;
                    //单独出现BF以下的，也算是GBK
                    if (0x80