Class diagrams Terézia Mézešová

Class diagram static diagram, part of UML describing classes structure of system shows classes, their attributes and methods and relationships between classes classes represent main interactions in system and classes to be programmed

Classes name attributes methods abstract classes have name in italics

Attribute and method syntax visibility name : data_type visibility name ( parameter_name : parameter_type, ... ) visibility: +   public -    private #   protected /   derived _   static

Relationships class level: generalization realization instance level: association aggregation composition

Generalization "is a" relationship, inheritance instance of subtype is also instance of superclass

Realization one element realizes the behavior of second element e.g. relationship between classes and interfaces showing that the class realizes methods offered by the interface

Association represents static relationship between objects of two classes

Aggregation "has a" relationship type of association relationship can only involve two classes

Composition "owns a" relationship stronger than aggregation if the container class is destroyed, all contained classes must be destroyed as well

Other types of relationships dependency - one class uses another at some point multiplicity: 0..1 - no or one instance 1 - exactly one instance 0..* - zero or more instances 1..* - at least one or more instances

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