Felix Grund
Instructor @ UBC
A5: Multiple Interfaces
CPSC 210
Learning Goals
-
Using multiple interfaces
- to allow you to declare multiple super types for a class
-
to state that some code uses an object
- from the perspective of one of those interfaces
I want to make any barking animal bark and I don't care if it's a dog or not!
for (Barking barker : barkers) {
barker.bark();
}
// "WOOOFF"
// "WUUUUUFFF"
// "WAAAAAFFF"
// "GRAAAA"
// "WOOOFF"Why Interfaces?
I want to make any barking animal bark and I don't care if it's a dog or not!
But dogs are not only bakers. They are also walkers...
Multiple Interfaces
void walk();
Dog
void fetchStick()
Fox
void fetchChicken()
Walking
void walk()<<interface>>
Barking
void bark()<<interface>>
Multiple Interfaces (2)
void makeThingBark(Barking barker) {
barker.bark();
}void makeThingWalk(Walking walker) {
walker.walk();
}Barking barkingWolf = new Wolf();
Walking walkingWolf = new Wolf();
Wolf explicitWolf = new Wolf();
makeThingBark(barkingWolf); // ???
makeThingWalk(barkingWolf); // ???
makeThingBark(walkingWolf); // ???
makeThingWalk(walkingWolf); // ???
makeThingBark(explicitWolf); // ???
makeThingWalk(explicitWolf); // ???Lecture Ticket Review
Bakery
void serveCookie()<<interface>>
CoffeeShop
void serveCookie()
void serveCoffee()<<interface>>
Kiosk
what method/s
must be implemented
in this class?
Lecture Ticket Review (2)
Bakery
void serveCookie()<<interface>>
CoffeeShop
void serveCookie()
void serveCoffee()<<interface>>
Kiosk
what method/s
must be implemented
in this class?
Lecture Ticket Review (3)
Bakery
void serveCookie()<<interface>>
CoffeeShop
void serveCookie()
void serveCoffee()<<interface>>
Kiosk
what method/s
must be implemented
in this class?
Lecture Lab: Learners
Lecture Lab
Which would compile?
Learner student = new Student();
student.getCourses();Student student = new Student();
student.getCourses();HasCourses somebodyWithCourses = new Student();
somebodyWithCourses.getCourses();B
A
C
Lecture Lab (2)
University uni = new University();
Learner learner = new Student();
uni.teach(learner);University uni = new University();
HasCourses somebodyWithCourses = new Student();
uni.teach(somebodyWithCourses);University uni = new University();
Student student = new Student();
uni.teach(student);A
B
C
public class University {
public void teach(
Learner learner) {
// ...
}
public void register(
HasCourses somebodyWithCourses) {
// ...
}
}Which would compile?
University uni = new University();
Learner learner = new Student();
uni.register(learner);D
University uni = new University();
Student student = new Student();
uni.register(student);E
University uni = new University();
HasCourses somebodyWithCourses
= new Student();
uni.register(somebodyWithCourses);F
A5: Multiple Interfaces
The End - Thank You!
CPSC210 - A5 Multiple Interfaces
By Felix Grund
