Object-Oriented Programming Concepts

Object-Oriented Concepts

• An object instance is a specific person, place, thing, or event, along with its attribute values.
• Objects have behavior, identity, and class (logical grouping of similar objects).
• Behavior refers to the actions an object can perform, also known as methods or operations.
• Identity refers to the uniqueness of an object, ensuring no two objects are the same.

Classes and Objects

• A class is a set of objects that share common attributes and behavior.
• Classes can be referred to as object classes or logical groupings.
• Objects can be instances of a class, inheriting its attributes and behavior.

Inheritance

• Inheritance is the concept where methods and/or attributes from one class can be reused by another class.
• Inheritance enables code reuse and facilitates a hierarchical relationship between classes.

Generalization/Specialization

• Generalization/specialization is a technique that groups common attributes and behaviors into a supertype class.
• The supertype class is inherited by other classes, which may contain unique attributes and behaviors.
• Supertype is also referred to as an abstract or parent class, while the inheriting classes are called subtypes or child classes.

Object/Class Relationships

• Object/class relationships refer to natural business associations between objects and classes.
• These relationships can be represented using UML notation.

Multiplicity and UML Multiplicity Notations

• Multiplicity refers to the minimum and maximum number of occurrences of one object/class for a single occurrence of a related object/class.
• UML notation is used to represent multiplicity in class diagrams.

Association and Aggregation

• Association refers to a natural business association between objects and classes.
• Aggregation is a relationship where a larger "whole" class contains one or more smaller "parts" classes.
• Composition is a type of aggregation where the "whole" is responsible for creating and destroying its "parts."

Messages and Polymorphism

• A message is communication that occurs when one object invokes another object's method to request information or action.
• Polymorphism is the concept that different objects can respond to the same message in different ways.
• Override is a technique where a subclass uses its own attribute or behavior instead of an inherited one.

Organizing Objects and Identifying Relationships

• To organize objects and identify relationships, follow these steps:
  • Identify associations and multiplicity
  • Identify generalization/specialization relationships
  • Identify aggregation relationships
  • Prepare the class diagram

Class Diagrams and Object Association Matrix

• A class diagram is a graphical depiction of a system's static object structure, showing object classes and their relationships.
• An object association matrix is a tool used to identify relationships between objects and classes.

Persistent and Transient Object Classes

• A persistent class describes an object that outlives the execution of the program that created it (e.g., stored in a database).
• A transient object class describes an object created temporarily by the program and lives only during its execution.