Question

Is there a difference in the meaning of “class diagram” and “object graph”?

Answer 1

see this tutorial
http://www.cs.toronto.edu/~jm/340S/Slides6/ClassD.pdf

Object graph contains value of one instance of class see example View its a view of an object system at a particular point in time

while

class diagram as wiki

The class diagram is the main building block of object oriented modelling. It is used both for general conceptual modelling of the systematics of the application, and for detailed modelling translating the models into programming code. Class diagrams can also be used for data modeling.[1] The classes in a class diagram represent both the main objects and or interactions in the application and the objects to be programmed. In the class diagram these classes are represented with boxes which contain three parts: [2]


A class with three sections.
The upper part holds the name of the class
The middle part contains the attributes of the class
The bottom part gives the methods or operations the class can take or undertake

see further