Implementing the Strategy Pattern in Java: A Case Study with Ducks

Discover how to correctly implement the `Strategy Pattern` in Java using practical examples involving flying ducks. Learn best practices and common pitfalls to avoid.
---
This video is based on the question https://stackoverflow.com/q/65337927/ asked by the user 'Sshawarma' ( https://stackoverflow.com/u/10085824/ ) and on the answer https://stackoverflow.com/a/65363727/ provided by the user 'jaco0646' ( https://stackoverflow.com/u/1371329/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Is this a correct implementation of the strategy pattern (JAVA, Fly method of ducks)?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Implementing the Strategy Pattern in Java: A Case Study with Ducks

The Strategy Pattern is a powerful design pattern that allows developers to define a family of algorithms, encapsulate each one, and make them interchangeable. It lets the algorithm's behavior vary independently from the clients that use it. In this guide, we're going to analyze a practical implementation of the strategy pattern using a Duck class that incorporates different flying strategies and see how to refine this implementation for better effectiveness.

Problem Overview

In the provided Java code, there is a base class Duck that uses an interface to define its flying behavior. Two implementations of this interface have been created: SimpleFly, which allows the duck to fly, and NoFly, indicating that the duck cannot fly. The constructor for Duck assigns a fly strategy based on the species of the duck. The goal here is to ensure the implementation adheres to the principles of the strategy pattern while minimizing code duplication and enhancing maintainability.

Current Implementation and Output

The current implementation of the flying strategy consists of these main components:

Interface IFly: This defines a method fly() that is implemented by the strategies.

Concrete Strategies: Classes SimpleFly and NoFly implement the IFly interface, providing the actual flying behavior for different types of ducks.

Duck Class: The Duck class utilizes a switch statement to assign the appropriate flying strategy based on its species enum.

Sample Output

When the following code is executed:

[[See Video to Reveal this Text or Code Snippet]]

The output is:

[[See Video to Reveal this Text or Code Snippet]]

The implementation seems functional at first glance. However, there are areas for improvement.

Suggested Improvements to the Implementation

While the current implementation makes strides in avoiding code duplication, it is essential to refine some aspects to align more closely with the principles of the strategy pattern. Here are some suggested improvements:

1. Rename the Fly Method

It can be confusing to name the fly method fly() when it may also refer to situations where a duck cannot fly. Consider renaming the method to tryToFly() or provide documentation clarifying that it represents an attempt to fly. This aligns with the Liskov Substitution Principle, ensuring that derived classes can be substituted for their base classes without altering the correctness of the program.

2. Composition Over Inheritance

The Duck class currently uses a switch statement to assign fly strategies based on species. Instead, it should accept an instance of IFly directly in its constructor or set it through a setter method. This way, the design adheres to the strategy pattern more effectively by avoiding branching logic. For example:

[[See Video to Reveal this Text or Code Snippet]]

This method allows any duck to utilize any flying behavior passed to it without being tied to specific species.

3. Flexibility for Runtime Changes

Implementations of the fly behavior can also be designed to allow Ducks to change their flying strategy at runtime. For example, a duck could switch from a Soar strategy to a Glide strategy depending on the circumstances of the environment. This flexibility is a significant advantage for maintaining dynamic behavior in your application.

Conclusion

In conclusion, while the initial implementation of the strategy pattern for the Duck class in Java is functional, understanding the principles behind the strategy pattern can help refine and improve your code. By renaming methods for clarity, utilizing composition instead of inheritance, and enabling runt

Видео Implementing the Strategy Pattern in Java: A Case Study with Ducks канала vlogize