strategy

Strategy Pattern

The Strategy Pattern is a behavioral design pattern that defines a family of algorithms, encapsulates each one, and makes them interchangeable. It allows the algorithm to vary independently from the clients that use it.

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📖 What is the Strategy Pattern?

The Strategy Pattern encapsulates algorithms into individual classes and allows objects to dynamically switch between them at runtime.

Key features:

1. Encapsulation: Encapsulates related algorithms into separate classes.
2. Flexibility: Allows dynamic swapping of algorithms during runtime.
3. Open/Closed Principle: Supports adding new algorithms without modifying existing code.

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🤔 Why Use the Strategy Pattern?

1. Dynamic Behavior: When the behavior of an object needs to change dynamically.
2. Avoid Conditional Logic: Eliminates the need for multiple if-else or switch statements.
3. Reusability: Promotes reusability by isolating algorithms in their own classes.

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🔧 Implementation

The implementation of the Strategy Pattern can be found in:

• FlyBehavior.java, QuackBehavior.java: Interfaces defining different behaviors.
• FlyWithWings.java, FlyNoWay.java: Concrete flying behaviors.
• Quack.java, Squeak.java: Concrete quacking behaviors.
• Duck.java: Base class for ducks, delegating behaviors to strategy objects.
• RubberDuck.java, MallardDuck.java: Concrete ducks with specific behaviors.
• Main.java: Demonstrates the usage of the Strategy Pattern.

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🛠️ Example Usage

To see the Strategy Pattern in action, refer to the Main.java file. It demonstrates how ducks dynamically change their flying and quacking behaviors.

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🌐 Real-World Examples

• Sorting Algorithms:
  • Switching between different sorting strategies (e.g., QuickSort, MergeSort) at runtime.
• Payment Systems:
  • Dynamically selecting a payment method (e.g., credit card, PayPal) at checkout.
• Game Characters:
  • Allowing characters to change behaviors dynamically (e.g., attack, defend).

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📊 UML Diagram

classDiagram
direction LR
    class Client {
    }

    class Context {
        -strategy : Interface
    }

    class Interface {
        +algorithm()
    }

    class ImplementationOne {
        +algorithm()
    }

    class ImplementationTwo {
        +algorithm()
    }

    Client --> Context
    Context o--> Interface
    Interface <|-- ImplementationOne
    Interface <|-- ImplementationTwo

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Note

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

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📝 Key Takeaways

• The Strategy Pattern encapsulates algorithms and allows them to be interchangeable.
• It simplifies code by removing complex conditional logic.
• Use it when objects need to support a variety of interchangeable behaviors.

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