Applied Design Patterns with Java

Behavioral :: Iterator (257) {C ch 19}

Applicability

Use the Iterator pattern:

• to access an aggregate object's contents without exposing its internal representation.
• to support multiple traversals of aggregate objects.
• to provide a uniform interface for traversing different aggregate structures (that is, to support polymorphic iteration).

Structure

Participants

• Iterator defines an interface for accessing and traversing elements.
• ConcreteIterator implements the Iterator interface, and keeps track of the current position in the traversal of the aggregate.
• Aggregate defines an interface for creating an Iterator object.
• ConcreteAggregate implements the Iterator creation interface to return an instance of the proper ConcreteIterator.

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