1. CSC 205 Java Programming II Abstract Data Type

2. Abstraction • The meaning of abstraction 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 denotesthe 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 • Lists • Queues • Stacks • Trees • Binary trees • Maps • Dictionaries • Sets

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