android 使用MD5加密文件

private static final int STREAM_BUFFER_LENGTH = 1024;private static final String ALGORITHM_MD5 = "MD5";

public static String md5File(File file) {
        if (null == file) {
            return "";
        }
        String result = "";
        try {
            MessageDigest digest = MessageDigest.getInstance(ALGORITHM_MD5);
            byte[] digests = updateDigest(digest, new FileInputStream(file)).digest();
            BigInteger bi = new BigInteger(1, digests);
            result = bi.toString(16);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

    public static MessageDigest updateDigest(final MessageDigest digest, final InputStream data) throws IOException {
        final byte[] buffer = new byte[STREAM_BUFFER_LENGTH];
        int read = data.read(buffer, 0, STREAM_BUFFER_LENGTH);

        while (read > -1) {
            digest.update(buffer, 0, read);
            read = data.read(buffer, 0, STREAM_BUFFER_LENGTH);
        }
        return digest;
    }