Object is a superclass for every java class because all classes required the
properties of object if you create a class

java.lanag.Object fully classified class name

Because every class is subclass of object you can place user defined objects
in collection frame work classes. if object is not a super class then you cannot
put your object in collection classes ed: they void method signature

public void add(Object 0)

If you are using this method you can place your objects because your class
derived from object class and also wait notify notify all methods used in
threading and String to String() method you have to override to display object
as string

int hasgCode to get hascode if you override this methods then only you can
add your class in Hash table object for component oriented programming toString
and hascode must be overrided derived from Object class

Because Java soft people wanted Hirarichy to maintain.
There should not be 2 base classes as it leads confusion to the programmar so every class is child of Object.