Java如何获取文件的字符集？

Java获取文件的字符集

/**
 * 获取文件的字符集
 *
 * @param file
 * @return
 */
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-16LE";
            checked = true;
        } else if (first3Bytes[0] == (byte) 0xFE
                && first3Bytes[1] == (byte) 0xFF) {
            charset = "UTF-16BE";
            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 <= read && read <= 0xBF)
                    break;
                if (0xC0 <= read && read <= 0xDF) {
                    read = bis.read();
                    if (0x80 <= read && read <= 0xBF)// 双字节 (0xC0 - 0xDF)
                        // (0x80 -
                        // 0xBF),也可能在GB编码内
                        continue;
                    else
                        break;
                    // 也有可能出错，但是几率较小
                } else if (0xE0 <= read && read <= 0xEF) {
                    read = bis.read();
                    if (0x80 <= read && read <= 0xBF) {
                        read = bis.read();
                        if (0x80 <= read && read <= 0xBF) {
                            charset = "UTF-8";
                            break;
                        } else
                            break;
                    } else
                        break;
                }
            }

        }
        bis.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return charset;
}