Why does every object in Java implicitly extend java.lang.Object class?

Question

I have been programming in Java for quite some time, but when I tried to explain what an java.lang.Object class is to a friend, I could not come up with more th

Answer 1

Every Class extends Object class implicitly so that they provide basic features which according to Java recommendation every class should have. Such as clone(), equals(), hashCode(), toString(), etc.

By implicitly, it means that if you are not extending any class then only compiler will implicitly extends Object class.But if class already extends other class then compiler will not extend Object class. For eg. Class A{ }

Class B extends A{ }

Here compiler will implicitly add extends Object class in class A declaration.

Class A extends Object{ }

Class B extends A{ }

As class A extends Object class so it will provide basic functionality of Object class such as equals(), toString(),etc. And since Class B extends class A which implicitly extends Class Object, so class B also provides all those features.

Thus by following this approach every class objects(variables) complies to features which every Java Object should have, without going for Multiple Inheritance (a class extending more than one class) which Java doesn't allows. This approach follows Multi-Level Inheritance.

Answer 2

Object class is the most super class of java programming, It has predefined methods according to types, you can use those methods. & you don't need to extends object class anymore & anywhere it's implicitly there

Answer 3

This is done so as most of the basic functions like toString() etc would be automatically inherited and to your next question this is NOT multiple inheritence it is multilevel inheritence... In multiple inheritence single class is derived from 2 or more base class whereas in multilevel as you have said it has a base class which is itself derived from Object class

Answer 4

It's a java design decision. It puts to use the concept of inheritance and re-usabilty. This ensures that all classes have some basic methods like wait(), toString() etc.