Calculating Checksum

The file upload methods require a checksum (which is a SHA-256 hash of the file’s content) to ensure that the binary content is transferred correctly. Java SDK contains the utility class, Checksum, which calculates the checksum for a file.

You can use the following code sample to calculate checksum:

    import java.security.*;
    ...
    try (FileInputStream fis = new FileInputStream(file)) {
        MessageDigest md;
        try {
            md = MessageDigest.getInstance("SHA-256");
        }
        catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }

        byte[] mdbytes;
        {
            byte[] buf = new byte[1024];
            int nread;
            while ((nread = fis.read(buf)) != -1)
                md.update(buf, 0, nread);
            mdbytes = md.digest();
        }

        StringBuilder rv = new StringBuilder();
        for (byte mdbyte : mdbytes)
            rv.append(Integer.toString((mdbyte & 0xff) + 0x100, 16).substring(1));

        return rv.toString();
    }