20.5. Container/Collection Classes in Code
It is often necessary for an object to maintain visibility to a group of other objects; the need for this is usually evident from the multiplicity value in a class diagram—it may be greater than one. For example, a Sale must maintain visibility to a group of SalesLineItem instances, as shown in Figure 20.9.
Figure 20.9. Adding a collection.
In OO programming languages, these relationships are often implemented with the introduction of a intermediate container or collection. The one-side class defines a reference attribute pointing to a container/collection instance, which contains instances of the many-side ...
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