The Object class sits at the top of the class hierarchy 
tree in the Java development environment. Every class in 
the Java system is a descendent (direct or indirect) of the 
Object class. The Object class defines the basic state and 
behavior that all objects must have, such as the ability to 
compare oneself to another object, to convert to a string, 
to wait on a condition variable, to notify other objects 
that a condition variable has changed, and to return the 
object's class.

object class is a base class for all class in java.using 
this class we can call from  super class  methods and 
variables to sub class

listen first , when you create object of one class which is not extending any class than , instead of one object , two object will be created and that is nothing but object of Object class and one more thing is no object is created with out it's superclass. So, object of subclass can not be created without it's superclass where Object class comes into picture because by default compiler gives Object class as superclass to all class which is not extending any class at compilation time itself.