iterator

Iterator Pattern

The Iterator Pattern is a behavioral design pattern that provides a way to access the elements of a collection sequentially without exposing its underlying representation.

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📖 What is the Iterator Pattern?

The Iterator Pattern decouples the iteration logic from the collection itself. It provides a standard interface for traversing a collection without knowing its internal structure.

Key features:

1. Encapsulation: Hides the complexity of traversal logic.
2. Consistency: Provides a standard way to access elements.
3. Flexibility: Supports different types of collections.

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🤔 Why Use the Iterator Pattern?

1. Abstraction: Decouples iteration logic from the collection's internal structure.
2. Flexibility: Supports multiple ways to traverse a collection.
3. Readability: Simplifies code by abstracting traversal logic.

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🔧 Implementation

The implementation of the Iterator Pattern can be found in:

• Iterator.java: Interface defining the traversal methods.
• Collection.java: Represents a collection of elements.
• ConcreteIterator.java: Concrete implementation of the iterator.
• ConcreteCollection.java: Concrete implementation of the collection.
• Main.java: Demonstrates the usage of the Iterator Pattern.

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🛠️ Example Usage

To see the Iterator Pattern in action, refer to the Main.java file. It demonstrates traversing a collection using an iterator.

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🌐 Real-World Examples

• Java Collections Framework:
  • Iterators are used to traverse collections like ArrayList or HashSet.
• Game Development:
  • Traversing game objects or scenes in a game engine.

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📊 UML Diagram

classDiagram
    class Aggregate {
        +CreateIterator()
    }

    class ConcreteAggregate {
        +CreateIterator()
    }

    class Iterator {
        +First()
        +Next()
        +hasNext()
    }

    class ConcreteIterator {
        +First()
        +Next()
        +hasNext()
    }

    Client --> Iterator
    Client --> Aggregate
    Aggregate <|-- ConcreteAggregate
    Iterator <|-- ConcreteIterator
    ConcreteAggregate --> ConcreteIterator : constructs
    ConcreteIterator --> ConcreteAggregate : has (traverses)

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Note

If the UML above is not rendering correctly, you can view the diagram from the iterator_uml.png file.

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📝 Key Takeaways

• The Iterator Pattern separates traversal logic from the collection's structure.
• It simplifies traversal and supports multiple traversal algorithms.
• Use it when you need to access elements of a collection without exposing its internals.

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