[java] 比较文件md5

   public class MD5 {
    private static final String TAG = "MD5";
 
    public static boolean checkMD5(String md5, File updateFile) {
        if (TextUtils.isEmpty(md5) || updateFile == null) {
            Log.e(TAG, "MD5 string empty or updateFile null");
            return false;
        }
 
        String calculatedDigest = null;
  try {
   calculatedDigest = calculateMD5(updateFile);
  } catch (Exception e) {
   e.printStackTrace();
  }
  
        if (calculatedDigest == null) {
            Log.e(TAG, "calculatedDigest null");
            return false;
        }
 
        Log.v(TAG, "Calculated digest: " + calculatedDigest);
        Log.v(TAG, "Provided digest: " + md5);
 
        return calculatedDigest.equalsIgnoreCase(md5);
    }
 
    public static String calculateMD5(File updateFile) {
        MessageDigest digest;
        try {
            digest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            Log.e(TAG, "Exception while getting digest", e);
            return null;
        }
 
        InputStream is;
        try {
            is = new FileInputStream(updateFile);
        } catch (FileNotFoundException e) {
            Log.e(TAG, "Exception while getting FileInputStream", e);
            return null;
        }
 
        byte[] buffer = new byte[8192];
        int read;
        try {
            while ((read = is.read(buffer)) > 0) {
                digest.update(buffer, 0, read);
            }
            byte[] md5sum = digest.digest();
            BigInteger bigInt = new BigInteger(1, md5sum);
            String output = bigInt.toString(16);
            // Fill to 32 chars
            output = String.format("%32s", output).replace(' ', '0');
            return output;
        } catch (IOException e) {
            throw new RuntimeException("Unable to process file for MD5", e);
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                Log.e(TAG, "Exception on closing MD5 input stream", e);
            }
        }
    }
}