When to use Strategy pattern in Java?

When to use Strategy pattern in Java?

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The Strategy pattern is a behavioral design pattern that enables an algorithm's variation without changing its code. It allows for implementing different strategies, which encapsulate algorithms and their data, allowing them to be interchanged easily.

In Java, the Strategy pattern can be applied in various scenarios where you need to change the behavior of an object at runtime or make it adaptable to different situations. Here are some common use cases:

When to use the Strategy pattern in Java? You should consider using this pattern when:

By applying the Strategy pattern, you can create a more flexible and extensible design that allows for easy adaptation to different scenarios without modifying the core logic of your application.

What is the difference between strategy and state design pattern in Java?

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Now, let's dive into the difference between strategy and state design patterns in Java.

Strategy Pattern

The Strategy pattern is a behavioral design pattern that enables you to define a family of algorithms, encapsulate each one, and make them interchangeable. This allows you to change the algorithm used without affecting the rest of the system.

In Java, the Strategy pattern typically involves an abstract strategy interface, concrete strategy classes that implement this interface, and a context class that uses these strategies. The context class can be modified to use different strategies at runtime, making it a flexible way to manage algorithms.

For example, consider a payment processing system that needs to handle various payment methods like credit cards, PayPal, or bank transfers. You could create separate strategy classes for each payment method and implement the payment logic within each class. Then, you can inject these strategies into your payment processor class and use them as needed.

State Pattern

The State pattern is a behavioral design pattern that allows an object to alter its behavior when its internal state changes. This pattern helps you manage complex state machines by encapsulating the state and behavior within a single class.

In Java, the State pattern typically involves an abstract state interface, concrete state classes that implement this interface, and a context class that uses these states. The context class can be modified to change its internal state at runtime, which affects its behavior.

For example, consider a vending machine that dispenses snacks or drinks based on the user's selection. You could create separate state classes for each product (e.g., SnackState, DrinkState) and implement the logic for dispensing each product within each state class. Then, you can set the initial state of the vending machine to an empty state and use it to manage the transitions between different states.

Key differences

Here are the key differences between Strategy and State patterns:

In summary, the Strategy pattern is about managing algorithmic changes, while the State pattern is about managing state transitions and complex state machines. While both patterns are useful in specific situations, they serve distinct purposes and should be applied accordingly.