Exception when calling

Question

I would like to ask a question for computing a hashvalue for a empty file. I need to compute a hash_value when the file f is first created and is empty. Then, at the end I will update the hash_value again. My code is not working for windows os. Can you tell me how to handle this? Thanks.

            objectFile = File(fullFilePath);
            fileInputStream = FileInputStream(objectFile);
            data = IOUtils.toString(fileInputStream, 'UTF-8');

            persistent digest;            

            if isempty(digest)
                digest = MessageDigest.getInstance('SHA-256');
            end

            hash = digest.digest(java.lang.String(data).getBytes('UTF-8'));

Error Message

    digest.digest(java.lang.String(data).getBytes('UTF-8'))
    Java exception occurred:
    java.lang.NullPointerException

        at java.security.MessageDigest.update(Unknown Source)

        at java.security.MessageDigest.digest(Unknown Source)

Your code doesn't even come close to compiling, for a start. — Joe C, Feb 20 '17 at 22:28
either digest or data is null. As "NullPointerException" reference. — Quintium, Feb 20 '17 at 22:43

score -1 · Accepted Answer · answered Feb 20 '17 at 22:45

-1

It looks like data is null, so instead of the following statement:

hash = digest.digest(java.lang.String(data).getBytes('UTF-8'));

Can you write this:

if isEmpty(data)
    hash = 0;
else
    hash = digest.digest(java.lang.String(data).getBytes('UTF-8'));
end

answered Feb 20 '17 at 22:45

Darshan Mehta

30,102
11
68
102

@downvoter reason for downvote? – Darshan Mehta Feb 21 '17 at 07:57

Exception when calling

1 Answers1