/**
* Answer the string described by the value of the unique optional <code>classProperty</code>
* property of <code>root</code>, or null if there's no such property. The value may be a URI, in
* which case it must be a <b>java:</b> URI with content the class name; or it may be a literal,
* in which case its lexical form is its class name; otherwise, BOOM.
*/
public static String getOptionalClassName(Resource root, Property classProperty) {
RDFNode classNode = getUnique(root, classProperty);
return classNode == null
? null
: classNode.isLiteral()
? classNode.asNode().getLiteralLexicalForm()
: classNode.isResource() ? mustBeJava(classNode.asNode().getURI()) : null;
}