Interfaces and all that, Quizzes of Computer Science

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Interfaces and all that;

Thoughts on Hashing

Ch. 6

Quiz directions

Individual section

Circle correct answer for each question

You get 2 tries for each question

Correct on 1st try (top line): 3 pts

Correct on 2nd try (bottom line): 1 pt

Keep your answers! (On quiz sheet)

Hand in sheet when complete

Group section

Start when all members of group are done w/ individual

Again, 2 tries

Grade yourselves as you go along

Hand in final group sheet

Why all the complexity?

Why two interfaces, an abstract class, and a bunch of concrete classes?

Common OO design principle

Interface : provides a contract or specification of what an object should be able to do

Has no data of its own

AbstractClass : provides “most” of the implementation of an interface

Takes grunt work out of instantiating an interface

May not be the most efficient possible

Concrete Class : provides everything necessary to use

Interchangability

Common view of interfaces:

“Interfaces are Java’s kludge to get around the lack of multiple inheritance”

WRONG!

(mostly)

Interfaces describe properties of a thing -- how you can use it

Any two objects that obey the same interface are (should be) semantically interchangeable

Can plug either in to same place and have function of program remain same

They may support diff extra stuff, side effects, have different efficiencies, etc.