The diamond problem only applies to implementation inheritance (extends in all versions of Java prior to Java 8). It doesn’t apply to API inheritance (implements in all versions of Java prior to Java 8). Since interface methods with matching type signatures are compatible, there is no diamond problem if you inherit the same method signature … Read more
Its not the same problem. In the original problem, the overriden method can be called from A. In your problem this can’t be the case because it does not exist. In the diamond problem, the clash happens if class A calls the method Foo. Normally this is no problem. But in class D you can … Read more
Most likely this is a XY problem. But … just don’t call it twice. #include <iostream> class Creature { public: virtual void identify() { std::cout << “I’m a creature” << std::endl; } }; class Swimmer : public virtual Creature { public: virtual void identify() override { Creature::identify(); tell_ability(); std::cout << “I’m a swimmer\n”; } virtual … Read more
Everything is absolutely valid. A compiler is allowed to warn about valid code, no problem here. You can try silencing the warning with a using declaration. If this doesn’t work (probably due to an MSVC bug), silence it with a pragma.
Someone else can find the standard quote but I’m going to explain conceptually. It doesn’t work because a using-declaration only affects name lookup. Your using-declaration causes name lookup to succeed where it would otherwise fail, that is, it tells the compiler where to find the function f. But it does not tell it which A … Read more
Interfaces cannot have state associated with them. Abstract classes can have state associated with them. Furthermore, default methods in interfaces need not be implemented. So in this way, it will not break already existing code, as while the interface does receive an update, the implementing class does not need to implement it. As a result … Read more
Well, when dealing with multiple inheritance in general, your base classes (unfortunately) should be designed for multiple inheritance. Classes B and C in your example aren’t, and thus you couldn’t find a proper way to apply super in D. One of the common ways of designing your base classes for multiple inheritance, is for the … Read more
You want: (Achievable with virtual inheritance) A / \ B C \ / D And not: (What happens without virtual inheritance) A A | | B C \ / D Virtual inheritance means that there will be only 1 instance of the base A class not 2. Your type D would have 2 vtable pointers … Read more
You could create interfaces for animal classes (class in the biological meaning), such as public interface Equidae for horses and public interface Avialae for birds (I’m no biologist, so the terms may be wrong). Then you can still create a public class Bird implements Avialae { } and public class Horse implements Equidae {} and … Read more