How to Generate an Md5 Checksum for a File in Android

How to generate an MD5 checksum for a file in Android?

Convert the file content into string & use the below method:

public static String getMD5EncryptedString(String encTarget){
        MessageDigest mdEnc = null;
        try {
            mdEnc = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Exception while encrypting to md5");
            e.printStackTrace();
        } // Encryption algorithm
        mdEnc.update(encTarget.getBytes(), 0, encTarget.length());
        String md5 = new BigInteger(1, mdEnc.digest()).toString(16);
        while ( md5.length() < 32 ) {
            md5 = "0"+md5;
        }
        return md5;
    }

Note that this simple approach is suitable for smallish strings, but will not be efficient for large files. For the latter, see dentex's answer.

How to get a file directory's MD5 checksum in Android/Java

As far as I know there isn't an efficient way to get the checksum of a directory.

md5 checksum on file in android doesn't match the md5 after i email it to myself

Found this answer here: How to generate an MD5 checksum for a file in Android?

public static String fileToMD5(String filePath) {
InputStream inputStream = null;
try {
    inputStream = new FileInputStream(filePath);
    byte[] buffer = new byte[1024];
    MessageDigest digest = MessageDigest.getInstance("MD5");
    int numRead = 0;
    while (numRead != -1) {
        numRead = inputStream.read(buffer);
        if (numRead > 0)
            digest.update(buffer, 0, numRead);
    }
    byte [] md5Bytes = digest.digest();
    return convertHashToString(md5Bytes);
} catch (Exception e) {
    return null;
} finally {
    if (inputStream != null) {
        try {
            inputStream.close();
        } catch (Exception e) { }
    }
}
}

private static String convertHashToString(byte[] md5Bytes) {
String returnVal = "";
for (int i = 0; i < md5Bytes.length; i++) {
    returnVal += Integer.toString(( md5Bytes[i] & 0xff ) + 0x100, 16).substring(1);
}
return returnVal;
}

Getting a File's MD5 Checksum in Java

There's an input stream decorator, java.security.DigestInputStream, so that you can compute the digest while using the input stream as you normally would, instead of having to make an extra pass over the data.

MessageDigest md = MessageDigest.getInstance("MD5");
try (InputStream is = Files.newInputStream(Paths.get("file.txt"));
     DigestInputStream dis = new DigestInputStream(is, md)) 
{
  /* Read decorated stream (dis) to EOF as normal... */
}
byte[] digest = md.digest();

A Simple MD5 Checker Android Apps

MD5 Hash function:

public static final String md5(final String s) 
    {
        try 
        {
            MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
            digest.update(s.getBytes());
            byte messageDigest[] = digest.digest();

            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < messageDigest.length; i++) 
            {
                String h = Integer.toHexString(0xFF & messageDigest[i]);
                while (h.length() < 2)
                    h = "0" + h;
                hexString.append(h);
            }
            return hexString.toString();
        }

        catch (NoSuchAlgorithmException e) 
        {
            e.printStackTrace();
        }
        return "";
    }

Getting a different MD5 check sum for the same file which is saved in different folder

Yes MD5 checkSum of a file depends on the location where you saved it.

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