SHA-256 is the recommended stronger alternative to SHA-1. See FIPS PUB 180-4 for implementation details.

Either by using a dedicated library or implementing the algorithm in your language, show that the SHA-256 digest of the string "Rosetta code" is: 764faf5c61ac315f1497f9dfa542713965b785e5cc2f707d6468d7d1124cdfcf

def sha256Hash = { text ->
    java.security.MessageDigest.getInstance("SHA-256").digest(text.bytes)
            .collect { String.format("%02x", it) }.join('')
}