multiple inheritance

Question 1

how to incorporate multiple inheritance in c++?

Answer 1

class A: public B1, public B2 {}

Question 2

how do data members in interfaces work?

Answer 2

any data members in an interface are automatically public, static, and final (like constants)

Question 3

how to incorporate multiple inheritance in java?

Answer 3

not possible for classes, but classes can have multiple interfaces (also interfaces can extend other interfaces)

Question 4

what if 2 interfaces provide the same constant?

Answer 4

user will need to specify which version it is (X.NUM or Y.NUM)

Question 5

what are 3 ways to simulate multiple inheritance in java?

Answer 5

1) interfaces

2) duplicate code (bad solution)

3) use limitation - insert objects lower into hierarchy, override methods we dont want (bad)

Question 6

in c++, what happens if a subclass with 2 super classes A and B both have the same method? how to call one or the other?

Answer 6

need to call it explicitly:

C c;
c.B::foo();

• not a problem if method signatures are different

Question 7

what the diamond problem?

Answer 7

say we have a hierarchy where A is a superclass of both B1 and B2, and C is a subclass of both B1 and B2:

then, c has 2 copies of A’s data

Question 8

for the diamond problem with A, B1, B2, and C, how to call B1’s version of a protected field “a”?

Answer 8

BA::a = 6;

Question 9

in the diamond problem for C++, what if i dont want 2 copies of A in C?

Answer 9

inherit A virtually in B1 and B2:
class B1: public virtual A{…}

• now C is responsible for creating A’s members in C