I have two classes, Class A and Class B. Class A is implicitly extending the Class Object. Now if Class B extending the Class A, Class B also extending the Object Class, so it is violating the multiple inheritance concept in java right? how it is possible.?
No, multiple inheritance is extending two classes at the same level. In your example, the base classes are not at the same level.
Please do a search for "multiple inheritance" in the forums here; this topic is discussed regularly here, and your question has been asked often. If you do a search you will find a list of answers very quickly.