Notes on "Java Design Patterns"-Chapter 2 UML Quick Introduction

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This blog is my notes after studying "Java Design Patterns". It is intended to facilitate review and review, and is not for commercial use.

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1. UML definition

• Unified Modeling Language (English: Unified Modeling Language, abbreviated UML)
• Non-patent third-generation modeling and specification language

2. UML Features

• UML is a development method

• A development method used to illustrate, visualize, construct, and write an object-oriented, software-intensive system product under development.

• UML demonstrates a series of best engineering practices

  These best practices have been proven effective in modeling large-scale and complex systems, especially at the software architecture level

3. UML2.2 Classification

A total of 14 icons are defined in UML2.2, which are classified as follows:

• Structural graphics: Emphasis is on systematic modeling
• Behavioral graphics: Emphasize the events triggered in the system model
• Interactive graphics: Belongs to the behavioral graphics sub-collection, emphasizing the data flow in the system model.

Structural graphics:

• Static diagram (class diagram, object diagram, package diagram)
• Implementation diagram (component diagram, deployment diagram)
• Section view
• Composite structure diagram

Behavioral graphics:

• Activity diagram
• State diagram
• Use case diagram

Interactive graphics:

• Communication diagram
• Interactive overview diagram (UML2.0)
• Timing diagram (UML2.0)
• Time chart (UML2.0)

4. UML class diagram

• Class Diagram: used to represent the static relationship between classes, interfaces, instances, etc.
• Although the name is a class diagram, the class diagram is not just a class, including permissions, attributes, methods, etc.

4.1 Arrow direction

UML arrow direction: from the child class to the parent class

4.2 Solid line-inheritance|dotted line-implementation

• Hollow triangle arrow: inheritance or realization
• The solid line-inheritance, is a relationship, the purpose of expansion, is not imaginary, very strong.
• Dotted line-realization, the dotted line represents the "virtual" no entity.

4.3 Solid line-association|dotted line-dependence

• Solid line-association relationship: stable relationship, real relationship, iron buddies.
• Indicates that a class object is related to another class object
• Usually one class has another class object as an attribute

• Dotted line-dependency: use it temporarily, if it is separated, illusory, if there is no
• Represents a kind of usage relationship, one class needs to use another class to realize the function
• Generally, one class uses another class as a parameter or as a return value

4.4 Hollow diamond-aggregation|solid diamond-combination

• The relationship between the whole and the part has an independent life cycle, which is the relationship of has a
• Weak relationship
• Negative words: weak-empty

• The relationship between the whole and the part is stronger than that of aggregation

  Both have the same life cycle, the relationship of contains-a

• Strong relationship

• Positive words: strong-full

Common number expressions and meanings, assuming there are A and B types, the numbers are marked on the A side:

• 0…1: 0 or 1 instance
• 0…*: 0 or more instances
• 1…1: 1 instance
• 1: There can only be 1 instance
• 1...*: At least 1 instance

5. UML timing diagram

• Sequence Diagram: is a diagram showing the interaction between objects, these objects are arranged in chronological order .
• The main modeling elements included in the sequence diagram are:
  • Object (Actor)
  • Lifeline
  • Focus of control
  • Message

6. Explanation of UML Class Diagram

The UML class diagram is divided into three parts:

• The name of the class
  • Ordinary class: GeelyClass
  • Abstract class (in italics): GeelyClass
  • Interface (indicated by angle brackets): << interface >>
• The attribute of the class, the symbol in front of the attribute indicates the access modifier
  • +：public
  • -：private
  • #：protected
  • ~：default
  • Underscore: static
• Class behavior

7. UML class diagram explanation-top-down