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();
	}