According to the coupling degree between classes from weak to strong, the class diagram in UML has the following relations: dependence, association, aggregation, combination, generalization and implementation. Among them, the degree of coupling between generalization and implementation is equal, which is the strongest.
Among them, the dependence relationship is the weakest, while the relationships represented by association, aggregation and combination are strengthened in turn. In other words, association, aggregation and combination are all dependencies. Aggregation is an association that represents the relationship between the whole and parts of an object, and combination is an aggregation that represents that the whole and parts have the same life cycle relationship.
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