Interview Questions On Java,Java EE


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Showing posts with label OOP Concepts. Show all posts
Showing posts with label OOP Concepts. Show all posts

Tuesday, April 10, 2007

What is the difference between Data Abstraction and Information Hiding?

Data Abstraction is often confused with information hiding while they altogether are two different technical concepts.Here are few established definitions of Data Abstraction:

"A view of a problem that extracts the essential information relevant to a particular purpose and ignores the remainder of the information." -- [IEEE, 1983]

"The essence of abstraction is to extract essential properties while omitting inessential details." -- [Ross et al, 1975]

"Abstraction is the selective examination of certain aspects of a problem. The goal of abstraction is to isolate those aspects that are important for some purpose and suppress those aspects that are unimportant." -- [Rumbaugh et al, 1991]

"An abstraction denotes the essential characteristics of an object that distinguish it from all other kinds of object and thus provide crisply defined conceptual boundaries, relative to the perspective of the viewer." -- [Booch, 1991]

While information hiding is not sharing the details of an object with outside world.Here are few standard definitions of Information Hiding which will elaborate more on this concept:

"The technique of encapsulating software design decisions in modules in such a way that the module's interfaces reveal little as possible about the module's inner workings; thus each module is a 'black box' to the other modules in the system." -- [IEEE, 1983]

"The process of hiding all the details of an object that do not contribute to its essential characteristics; typically, the structure of an object is hidden, as well as the implementation of its methods. The terms information hiding and encapsulation are usually interchangeable." -- [Booch, 1991]

"The principle of information hiding is central. It says that modules are used via their specifications, not their implementations. All information about a module, whether concerning data or function, is encapsulated with it and, unless specifically declared public, hidden from other modules." -- [Graham, 1991]
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What is Data Encapsulation?

Data Encapsulation is wrapping informations(attributes and behaviors) within an object.A suitable example is a class as it wraps methods and data within itself. The attributes of a class corresponds to its data members while behaviour corresponds to member methods of the class.
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What is Data Abstraction?

Data Abstraction is extraction of essential information for a particular purpose and ingnoring the remainder of the information,e.g. a car is consisted of an engine,air filters,a carburetor,a gear box,a steering,a fuel tank,tyres etc.A driver of a car need not to be bothered about several finer points of the car,he/she should know what it requires to drive a car.Take another user, a car mechanic, he will require different set of information in order to repair the car.
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Java and Object Oriented Analysis and Design Questions

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