title: Unified-Modeling-Language
date: 2023-11-02	
author:
  - AllenYGY
status: DONE
tags:
  - NOTE
  - Java
  - Lec1
  - Program
created: 2023-11-02T00:59
updated: 2024-05-31T01:02
publish: True

Unified-Modeling-Language

UML

Class diagrams
- Sequence diagrams
- Use case diagrams
- Activity diagrams

Class Diagram

Describe the system in terms of classes and their relationships.
Natural ways of reflecting the real-world entities and their relationships.

Class Relationship

Association (directional + Multiplicity)

Association represents a general binary relationship that describes an activity between two classes.

A class is aware of and holds a reference to another class.

Association

Bidirectional or Unidirectional
- Unidirection
- Bidirectional

Aggregation

A special type of association, which represents a “Has-A” relationship 空心菱形

They may have different life cycles.

Composition

Represents a “Part-of” relationship. 实心菱形

Life cycle of the part is dependent on the whole’s life cycle

Inheritance

Often referred as a “is-a” relationship. 三角空心

E.g., a dog is an animal.

Realization/Implementation

For interface

In Java, an interface is not a class but a set of requirements for classes that want to conform to the interface