Mastering Java: The Ultimate Quiz for 'Thinking in Java'

Calling the 'toString()' method on an Object that is not overridden will result in the class name and the object's hash code being outputted. This is because the 'toString()' method outputs a textual representation of an object, and if not overridden, it will default to the implementation provided by the Object class. This implementation includes the class name and the hash code, making option A the correct answer. Options B and C are incorrect because they do not pertain to the 'toString()' method or the default implementation for an Object. Option D is incorrect because the 'toString()' method does not return a blank string unless overridden to do so.