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Does Java support multiple inheritance, why or why not?

+1 vote
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Does Java support multiple inheritance, why or why not?
posted Apr 16, 2015 by anonymous

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2 Answers

+2 votes

No...Actually java does not support multiple inheritance.

Two reson:

1) First reason is ambiguity around Diamond problem, consider a class A has foo() method and then B and C derived from A and has there own foo() implementation and now class D derive from B and C using multiple inheritance and if we refer just foo() compiler will not be able to decide which foo() it should invoke. This is also called Diamond problem because structure on this inheritance scenario is similar to 4 edge diamond, see below

        A foo()
           / \
          /   \
   foo() B     C foo()
          \   /
           \ /
            D
           foo()

In my opinion even if we remove the top head of diamond class A and allow multiple inheritances we will see this problem of ambiguity.

Some times if you give this reason to interviewer he asks if C++ can support multiple inheritance than why not Java. hmmmmm in that case I would try to explain him the second reason which I have given below that its not because of technical difficulty but more to maintainable and clearer design was driving factor though this can only be confirmed by any of java designer and we can just speculate. Wikipedia link has some good explanation on how different language address problem arises due to diamond problem while using multiple inheritances.

2) Second and more convincing reason to me is that multiple inheritances does complicate the design and creates problem during casting, constructor chaining etc and given that there are not many scenario on which you need multiple inheritance its wise decision to omit it for the sake of simplicity. Also java avoids this ambiguity by supporting single inheritance with interfaces. Since interface only have method declaration and doesn't provide any implementation there will only be just one implementation of specific method hence there would not be any ambiguity.

answer Apr 16, 2015 by Karthick.c
+1 vote

No, Java doesn't support multiple inheritance because for Enterprise level application or big application it might get a bit complex to understand the flow. So, to reduce the complexity of any big application or design . Java doesn't support multiple inheritance. C++ Supports multiple Inheritance instead

answer Apr 17, 2015 by Gagan Shripad
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