multiple inheritance

[singh rajiv]

why java does not support multiple class inheritance. as c++ support.

help!!!

[salvin francis]

Is that a question ?
welcome to javaranch singh rajiv

[Jesper de Jong]

Because multiple inheritance causes complicated problems such as the diamond problem and because you rarely need multiple inheritance in practice.

The designers of the Java programming language wanted to make a language which was easier to use than C++, so they left out complicated and unnecessary features such as multiple inheritance.

Note that your question is a frequently asked question. Search the forums and you'll find lots of older discussions about why Java does not support multiple inheritance.

[salvin francis]

don't use 31 exclamation marks after a word (especially "help"), it freaks me out !!
I agree with Jesper Young over the complications part,

Imagine java with "virtual functions" !

I hope your next question is not on operator overriding ...

[David Newton]

Personally, I like multiple inheritance and miss it. I prefer other implementation patterns, like mixins or traits, but I don't feel as many do that multiple inheritance is inherently evil.

[fred rosenberger]

From what i've read, the designers thought that the headaches caused by multiple inheritance vastly outweighed any benefits gained by including it.

[Vishal Hegde]

java supports multilevel inheritence that is

one class can extend only one class

i think its made like this just to make it more security conciusnessor just to avoid duplication of variables from different classes or just to avoid errors like duplicate declaration of variables??

Also with the intro of interfaces ,i think its quite a good replacement for multiple inheritence

[Campbell Ritchie]

It's not supposed to have anything to do with variables, but with methods.

[Vishal Hegde]

Campbell Ritchie wrote:It's not supposed to have anything to do with variables, but with methods.

class a
{
           int a;
}
class b extends a
{
  
      int c,b;
void add()
{
  c=a+b;
}
}
class calculate
{  
 public static void main(String args[])
{
b b1=new b();
    b.a=1;
    b.b=2;
b.add();
}
}

sir we are accesiing variablle of a class using b's object? doesnt both variables and methods come into play?

[David Newton]

Vishal Hegde wrote:Also with the intro of interfaces ,i think its quite a good replacement for multiple inheritence

No, it's not; you still have to re-implement behavior. It avoids some pitfalls at the cost of repetition.

[Mohnish Khiani]

The diamond problem still exists with interfaces.....then why was multiple inheritence removed...was there any technical reason?

[David Newton]

Not really.

There's no implementation inheritance, so it doesn't matter which interface you're referring to--you can only implement one method with a given signature. No matter which interface your object is currently acting like it'll call the same implementation--no diamond problem. The diamond problem refers to implementation disambiguation.