Java Doubt on Multiple inheritance

Question

Java does not support multiple inheritance but Object class is by default super class of all classes. e.g

class Object
{

}
class B
{

}
class A extends B
{
}

Class A can access all method of B and Object.Is not it a example of multiple inheritance? So is it correct that Java does not support multiple inheritance.

my question is not to find difference between multilevel and multiple inheritance. Java Docs,it self says :Class Object is the root of the class hierarchy. Every class has Object as a super class. All objects, including arrays, implement the methods of this class. So it means Class Object is super class of Class A{Previous example}. But Class B is also Super Class of Class A. SO what is meaning of it ?

+1 Seems like a fair enough question about the meaning of multiple inheritance — krock
– krock, Commented Sep 26, 2011 at 9:44

KV Prajapati · Accepted Answer · 2011-09-26 09:40:50Z

7

It is know as transitive nature of Inheritance.

answered Sep 26, 2011 at 9:40

KV Prajapati

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Community · Accepted Answer · 2017-02-09 15:37:53Z

7

Look at the difference between transitive inheritance (C inherits directly from B and transitively from A):

transitive

and multiple inheritance (C inheriting from both A and B):

transitive

edited Feb 9, 2017 at 15:37

CommunityBot

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answered Sep 26, 2011 at 9:46

Tomasz Nurkiewicz

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2 Comments

user835281 Over a year ago

Correct me If I'm wrong. Here in the question Class B has java.lang.Object as its super class while Class A has Class B as its super class. Is the inheritance relationship between Class B and Class java.lang.Object is masked at Class A.

Navigateur Over a year ago

Nope, not masked, everything is just added on, except methods with the same signature, which are overridden. Even variables declared with the same name are added on, they're just said to be "hidden" but can still be accessed using casting, or the super keyword if it's the immediate parent. You wouldn't ever want to do this though, just give your variables different names and they're all added on without any hiding.

Nicola Musatti · Accepted Answer · 2011-09-26 09:41:24Z

4

No it isn't. Multiple inheritance is when a class has more than one direct base class, as in:

class A {}

class B {}

// not valid Java
class C extends A, B {}

A class may have many indirect base classes, each with only one direct base class, as in:

class D extends A {}

class E extends D {}

class F extends E {}

Here the inheritance hierarchy is F -> E -> D -> A -> Object, but this is still single inheritance.

answered Sep 26, 2011 at 9:41

Nicola Musatti

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Comments

Costis Aivalis · Accepted Answer · 2011-09-26 09:41:45Z

1

Since no Java class can extend directly two or more classes you can safely say that Java does not support multiple inheritance.

You would have multiple inheritance if you were able to say class A extends B, C, but you can never do that.

answered Sep 26, 2011 at 9:41

Costis Aivalis

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