private String assertHashAlgorithmName() throws IllegalStateException {
        String hashAlgorithmName = getHashAlgorithmName();
        if (hashAlgorithmName == null) {
            String msg = "Required 'hashAlgorithmName' property has not been set.  This is required to execute "
                    + "the hashing algorithm.";
            throw new IllegalStateException(msg);
        }
        return hashAlgorithmName;
    }
Returns the {@link #getHashAlgorithmName() hashAlgorithmName} property, but will throw an
{@link IllegalStateException} if it has not been set.

@return the required {@link #getHashAlgorithmName() hashAlgorithmName} property
@throws IllegalStateException if the property has not been set prior to calling this method.
@since 1.1
core/src/main/java/org/apache/shiro/authc/credential/HashedCredentialsMatcher.java