case 1

suppose you have a class Test, which doesn't extend any other class. So by default, Object becomes it's super class.

                                   Object->Test

case 2

If your Test class wants to extend some other class, for example Hashtable, your class will become a sub class of Object through Hashtable because Hashtable is a subclass of Object. Any class you are trying to extend will be a subclass of Object directly or due to hierarchy. 

                                    Object->Map->Hashtable->Test

Object is the superclass of Test even when you have Test extend HahTable

So according to case 1 Test is a subclass of Object directly.

According to case 2 Test is a subclass of Object due to the hierarchy.

so no matter you extend a class or not, your class will always be a subclass of Object.