Object Orientation detail in JAVA

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  • Object-oriented(OO) means that we organize software as a collection of isolated objects that incorporate both data structure and behavior.
  • Object Orientation is about viewing and modeling the word/system as a set of interacting and interrelated objects.
  • Characteristics of OO approach include four aspects: identity, classification, inheritance and polymorphism.

i. Identity

  • Identity means data is quantized into discrete and distinguishable entities. Each object is having its own inherent identity.
  • Objects are distinct even if all their attribute values are identical.
  • Objects can be concrete, such as a file in a file system, or conceptual, such as a scheduling policy in a multiprocessing operating system.

ii.Classification

  • Abstract entities with the same structure and behavior are grouped into classes.
  • A class is an abstraction that describes properties important to an application and ignores the rest.
  • Each class describes a possibly infinite set of individual objects.
  • Each object is said to be an instance of its class. 
  • Each class describe infinite set of individual object and each object is instance of class.

iii. Inheritance

  • Sharing of attributes and operations based on a hierarchical relationship.
  • Each subclass inherits all features of super class and adds its unique features.
  • A super class has general information that sub-classes refine and elaborate.
  • Each subclass incorporates, or inherits all the features of its super class and adds its own unique features.
  • Subclasses need not repeat the features of the super class.
  • Example, Scrolling Window, Fixed Window and subclasses of Window.

   iv. Polymorphism

  • Polymorphism means that the same operation may behave differently for different classes.
  • Polymorphism - a Greek term means ability to take more than one form.
  • The same operation may behave differently on different classes.
  • An operation is procedure or transformation that an object performs or is subject to.
  • Implementation of operation by a specific class is called method.