UML-idea

UML Classes and classes in 、 Classes and interfaces 、 The relationship between interfaces is ： generalization 、 relation 、 rely on 、 Realize these

generalization

• It refers to that one class inherits the functions of another class , And you can add your own new functions , stay java Keyword in extends To express
• Symbol ： arrow + Real triangle , as follows
  

Realization

• It is worth noting that a class implements one or more interfaces , stay java Keyword in implements To express
• Symbol ： Use dotted lines and real triangles to represent , as follows ：
  

rely on

• Dependency represents a weak connection between classes , Indicates that a class depends on the definition of another class , Dependencies are one-way . stay java in , Dependency manifests itself as ： local variable , Method 、 Calls to static methods .
• Symbol ： Dotted line + arrow
  

relation

• Associations represent strong connections between classes , It makes one class know the properties and methods of another class . The association has two endpoints , Each endpoint can have a cardinality , The class representing this association can have several instances .

  0…1 Indicates that there can be 0 A or 1 An example
  0…* Indicates that there is no limit on the number of instances
  1 Indicates that there can only be one instance
  1…* Indicates that there is at least one instance

• stay Java in , Association is implemented using instance variables

• Symbol ： Solid line + arrow
  

polymerization

• Aggregation is a special case of association , It's a strong correlation , Aggregation is the relationship between the whole and the individual , Now the whole and the part can be separated , They have their own life cycle , Parts can belong to multiple objects , It can also be shared by multiple objects ; Like computers and CPU, The relationship between the company and its employees ; Aggregation and association are consistent at the code level , It can only be distinguished semantically .

• Aggregation relationships are also implemented using instance variables , stay java There is no grammatical distinction between association and aggregation , The class in the association relationship comes from one level , And aggregation is obviously at two different levels .

• Symbol ： arrow + Solid line + Real diamond

Combine

• Combination is a special case of association , It embodies a kind of contain-a Relationship , Better than aggregation , It's a strong aggregation relationship . It also embodies the relationship between the whole and the part , But at this time, the whole and the part are inseparable , The end of the whole life cycle also means the end of part of the life cycle , vice versa . Like the brain and humans .

• Combination and aggregation are almost identical , The only difference is for the combination ,“ part ” Different from “ whole ” Exist alone , Its life cycle should be consistent .

• Symbol ： Solid line + arrow + The diamond

example ：