Prime Instance

Association Association is a simple relationship between two classes. For example A relationship between Professor Class and Student class is known as Association. Both Classes can exist without each other, so Professor and Student are two independent classes. In this kind of relationships there will not be any owner class. Both classes have their own life cycle. UML Notation:     Aggregation Aggregation is a special type of Association. It is known as “Has-A” relationship. For example A Department class can contain Professor Class. Here Department class is owner class. Here in this relationship even after deleting Department class, Professor Class can exits. UML Notation: Composition Composition is a special type of Aggregation. It is known as “Is-A” relationship. For example A University Class has many Department class. Here University and Department objects are dependent on each other. If we delete Univ...

Liskov Substitution Principle Definition 2 : Functions that use references to base classes must be able to use objects of derived classes without knowing it. Definition 2 : Object inheriting from base class or interface or other abstraction must be semantically substitutable for the original abstraction. Definition 3 : If a program module is using a Base Class, then the reference to the base class can be replaced with a derived class without affecting the functionality of the program module. Problem We all know that square is a rectangle from geometry. Now create a Rectangle base class with associated Height and Width properties and create Area() method to calculate the area in Rectangle base class.     public class Rectangle     {         public virtual int Height { get ; set ; }         public virtual int Width { get ; set ; }   ...

1.     Steps to create user or role in PostgreSQL ·         Open pgAdmin III ·         Login to PostgreSQL database ·         Select “Login Roles” and right click on mouse to view the context menu ·         Select “New Login Role” from context menu ·         Enter desired user name in “Role name” text box ·         Select “Definition” tab in “New Login Role” window ·         Enter desired Password in the given text box ·         Select “Role privileges” tab in “New Login Role” window ·         Select the privileges for the entered user or role ·         Select “SQL”...