1. Lecture 11 Abstract Data Type
CSC 205 Programming II
Lecture 11
Abstract Data Type

2. Abstraction The meaning of abstraction A definition by Grady Booch
Abstraction arises from a recognition of similarities between certain objects, situations, or processes in the real world, and the decision to concentrate upon these similarities and to ignore for the time being the differences
A definition by Grady Booch
An abstraction denotes the essential characteristics of an object that distinguish it from all other kinds of objects and thus provide crisply defined conceptual boundaries, relative to the perspective of the viewer

3. Abstraction

4. The Walls – abstraction barrier
An abstraction serves as an separation between an object’s behavior and its implementation – an abstraction barrier
It focuses on the outside view of an object and hide the implementation details
Deciding upon the right set of abstractions for a given domain is the central problem in OO design

5. The Walls – an example
The ice maker as an abstraction, has the following well-defined behaviors
Output
Crushed ice
Ice cubes
Chilled water
Indicate
Out-of-ice
Input
Water
The ice maker in a client’s view –
The ways how ice is made and how
the dispenser works is unknown

6. Client-Server Contracts
A collaboration is a one-way interaction between two objects: one plays the client role, the other plays the server role
A C-S contract is defined by the set of request that a client can make of a server (in terms of public methods in Java)
client
client
server
request
contract

7. Inside the Walls
Services defined in the contract is solely up to the server object
Structural elements – data members
Behavioral elements – methods
Java classes are good in implementing such abstractions
IceMaker
+chill()
+crush()
+cube()
+isEmpty()
+addWater()

8. Abstract Data Type An ADT is an abstraction of a data type, with
a collection of data, and
a set of operations on that data
Typical operations an ADT needs to support
Add data to a data collection
Remove data from a data collection
Inquiries about the data in the collection

9. What Is Not an ADT? An ADT is not a data processor
It’s not supposed to manipulated data
So an abstraction such as the ice maker is not a good example
It takes in water, and outputs something different

10. Various ADTs Linear ADTs Trees Maps Sets Dictionaries Lists Queues
Stacks
Trees
Binary trees
Maps
Sets
Dictionaries

11. The ADT List Operations supported Create Check if empty Determine size
Add items
Remove items
Retrieve items (at a given position)

12. A Sample Java Implementation
java.util.vector