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From: Jeff Higgins <jeff@invalid.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: can you give me some hints on the Oracle Java SE related certificates?
Date: Wed, 23 Sep 2015 10:54:07 -0400
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On 09/23/2015 09:43 AM, Eric Sosman wrote:
> On 9/23/2015 9:25 AM, Sebastian wrote:
>> Am 22.09.2015 15:50, schrieb Jerry Stuckle:
>> [snip]
>>> Multiple inheritance can be a very useful technique - one that I have
>>> used occasionally in C++.  The biggest problem I've seen with it is
>>> misuse.  But it's one I definitely miss in Java.
>>>
>> I think so far it has not been mentioned in this thread that Java does
>> have indeed multiple inheritance of behavior with default methods in
>> interfaces, since Java 8.
>
>      Only to the same extent as in earlier Java versions, though.
> All that Java 8 added was default implementations of the specified
> methods, not the (potential) multiple inheritance.
>
>      That is, even in Java 1 you could get into trouble:
>
>      interface Muggle {
>          void spell(String word);
>      }
>
>      interface Wizard {
>          void spell(String charm);
>      }
>
>      class Rowling implements Muggle, Wizard {
>          // Which kind of spell() should I implement?
>      }
>
> ... or even worse:
>
>      interface Machine {
>          /** Operate the machine. */
>          void operate();
>      }
>
>      interface Surgeon {
>          /** Return true iff the patient survives. */
>          boolean operate();
>      }
>
>      class Autodoc implements Machine, Surgeon {
>          // This class cannot be written
>      }
>
 From the JLS 8:

Example 8.1.5-3. Illegal Multiple Inheritance of an Interface
interface I<T> {}
class B implements I<Integer> {}
class C extends B implements I<String> {}
Class C causes a compile-time error because it attempts to be a subtype 
of both I<Integer>
and I<String>.

Bringing the overloaded term "Multiple Inheritance" into a beginning
Java programming course in a fashion such as "No multiple inheritance
in Java" and all of its variants is harmful. If you have to bring it in
at least do it as in the example provided by the Java tutorials. If a
particular student needs more information point him to it and carry on.

That is my opinion.