Strategy Design Pattern Tutorial with Java Coding Example | Strategy Pattern Explained

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24 Jan 202313:34

Summary

TLDRIn this episode of Goldman Digest, the focus is on the Strategy Design Pattern, a software design pattern that allows the behavior of an object to change at runtime. The video explains the concept, provides a Java implementation, and discusses its benefits, including adherence to the Open/Closed Principle and the ability to switch algorithms dynamically. Examples like transportation strategies and a navigation app illustrate the pattern's utility. The host encourages viewers to subscribe and engage with the content, promising a follow-up on the Observer Design Pattern in the next installment.

Takeaways

😀 The video introduces the Strategy Design Pattern, explaining its concept and applications.
🔍 It discusses where to use the Strategy Design Pattern in projects, highlighting its utility in software development.
💻 The presenter provides a Java code implementation of the Strategy Design Pattern, demonstrating its practical application.
🚀 The video emphasizes the benefits of using the Strategy Design Pattern, such as the ability to change algorithms at runtime.
📚 A real-world example is given to illustrate the Strategy Design Pattern, making it easier to understand its use cases.
🔗 The video links to a GitHub repository where viewers can access the code for the Strategy Design Pattern discussed.
📈 The presenter outlines scenarios where the Strategy Design Pattern is particularly useful, such as when multiple algorithms are needed.
🛠️ The video explains the Open/Closed Principle in the context of the Strategy Design Pattern, emphasizing code maintainability.
📝 The script encourages viewers to engage by subscribing, liking, and sharing the video, and to comment on their experiences with the pattern.
⏭️ The video concludes with a teaser for the next video, which will cover the Observer Design Pattern.

Q & A

What is a strategy design pattern?
-A strategy design pattern is a behavioral design pattern that enables an algorithm's behavior to be selected at runtime. It allows the definition of a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
What is the benefit of using the strategy design pattern?
-Using the strategy design pattern allows you to swap algorithms used inside an object at runtime, supports the open/closed principle by being open for extension but closed for modification, isolates the implementation detail of an algorithm from the code that uses it, and can replace inheritance with composition.
How does the strategy design pattern relate to the open/closed principle?
-The strategy design pattern exemplifies the open/closed principle by allowing new functionalities to be added (open for extension) without modifying existing code (closed for modification). This is achieved by adding new algorithm strategies without altering the context or other strategies.
Can you provide a real-world example of the strategy design pattern mentioned in the script?
-Yes, a real-world example given in the script is choosing a mode of transportation to the airport. Depending on factors like budget or time constraints, one might choose between a bus, a cab, or a bicycle, each representing a different strategy.
What is the context class in the strategy design pattern?
-The context class in the strategy design pattern is the driver class that encapsulates the strategy. It maintains a reference to one of the strategy objects and delegates the work to the linked strategy object instead of executing its own algorithms.
How does the strategy design pattern help in maintaining a navigation app as described in the script?
-The strategy design pattern helps in maintaining a navigation app by allowing the app to add new routing algorithms (like car, cyclist, or walking routes) without significantly increasing the complexity of the main class. It does this by delegating the routing logic to strategy objects, keeping the main class clean and manageable.
What is the role of the strategy interface in the strategy design pattern?
-The strategy interface in the strategy design pattern defines a common interface for all supported algorithms. It allows the context to work with all strategies because they are derived from the same interface, enabling the context to switch between different algorithms at runtime.
How can you add a new algorithm to the strategy design pattern without modifying existing code?
-To add a new algorithm without modifying existing code, you create a new class that implements the strategy interface and then instantiate this new strategy class when needed. The context can then use this new strategy object, adhering to the open/closed principle.
What is the difference between strategy pattern and state pattern as mentioned in the script?
-The strategy pattern is about defining a family of algorithms and making them interchangeable, whereas the state pattern allows an object to alter its behavior when its internal state changes. The strategy pattern is used to switch algorithms at runtime, and the state pattern is used to manage state transitions internally.
How does the script demonstrate the strategy design pattern with a calculator example?
-The script demonstrates the strategy design pattern with a calculator example by defining a strategy interface with a calculate method and various strategy implementations for addition, subtraction, multiplication, and division. The calculator context then uses these strategies to perform operations on numbers based on the selected strategy.

Outlines

00:00

🔑 Introduction to Strategy Design Pattern

The video begins with a warm welcome and an introduction to the topic: the Strategy Design Pattern. The host, Goldman Digest, sets the stage by discussing the importance of understanding design patterns, particularly the Strategy pattern. This pattern allows for the definition of a family of algorithms, encapsulated within separate classes, making them interchangeable. The video promises to cover the use cases, Java implementation, and benefits of this pattern. It also encourages viewers to engage by commenting on their understanding of the State Design Pattern from a previous video, with a link provided for those who missed it. The host invites viewers to subscribe to the channel for quality content and ends the introduction with a call to action for likes, shares, and subscriptions.

05:00

💡 Strategy Design Pattern Explained

This paragraph delves into the concept of the Strategy Design Pattern, illustrating how it enables the selection of an algorithm's behavior at runtime. The host explains that the pattern involves encapsulating related algorithms within a 'context' class, allowing the client program to choose the appropriate algorithm or have the context select it automatically. The pattern is exemplified with real-world scenarios, such as choosing transportation to the airport, and a navigation app that evolves to include different route planning strategies for cars, cyclists, and pedestrians. The paragraph emphasizes the pattern's utility in scenarios where algorithm selection needs to be dynamic and the benefits of adhering to the open-closed principle, which promotes extensibility without modifying existing code.

10:02

🛠 Implementation of Strategy Design Pattern

The host transitions into demonstrating the Strategy Design Pattern through a Java code example. The code, available on GitHub, showcases a 'calculator' scenario where different strategies for arithmetic operations (addition, subtraction, etc.) are implemented as separate classes. The 'calculator' class uses a strategy object to perform operations, allowing the operation to be changed at runtime. The video walks through the code, explaining the structure and the strategy interface, followed by concrete strategy classes for each arithmetic operation. The test class is then highlighted, which initializes the calculator with different strategies to perform calculations, demonstrating the flexibility of the pattern in action.

📈 Use Cases and Benefits of Strategy Design Pattern

The final paragraph summarizes the Strategy Design Pattern's applications and advantages. The host outlines scenarios where the pattern is particularly useful, such as when an object needs to use different algorithms or when there are many similar classes that differ only in execution. The benefits discussed include the ability to swap algorithms at runtime, adherence to the open-closed principle, isolation of algorithm implementation details, and the replacement of inheritance with composition. The video concludes with a teaser for the next topic, the Observer Design Pattern, and a call to action for viewers to subscribe, like, and share the video for more educational content.

Mindmap

Keywords

💡Strategy Design Pattern

A software design pattern that allows you to define a family of algorithms, encapsulate each one in a separate class, and make their objects interchangeable. It relates to the video's theme as the central topic being discussed, where different algorithms can be selected at runtime depending on the scenario. The presenter explains this pattern with examples of transportation choices and a navigation app that needs to adapt its route planning for cars, cyclists, and walkers.

💡Context Class

In the Strategy Design Pattern, the context class is responsible for interacting with the strategy (algorithm). It holds a reference to a specific strategy object and delegates the execution to that object. In the video, the context class was discussed as the 'calculator' class, which holds input numbers and applies a selected strategy like addition or subtraction.

💡Algorithm

An algorithm is a step-by-step procedure used for calculations, data processing, or automated reasoning tasks. In the Strategy Design Pattern, each strategy encapsulates a different algorithm. The video gives the example of algorithms such as addition, subtraction, multiplication, or division that can be selected at runtime based on the context class's input.

💡Open-Closed Principle

A design principle that states software entities should be open for extension but closed for modification. This principle is linked to the Strategy Design Pattern as the presenter explains that new algorithms can be added without modifying existing code, allowing for flexibility in extending functionality without disrupting the original design.

💡Runtime

The period when a program is executing. In the context of the Strategy Design Pattern, the choice of algorithm can be made at runtime, allowing dynamic behavior based on the circumstances. The presenter emphasizes how this flexibility is one of the main benefits of the strategy pattern, such as selecting addition or subtraction strategies when the program is already running.

💡Encapsulation

Encapsulation in software design involves bundling data with methods that operate on the data. In the Strategy Design Pattern, algorithms are encapsulated within their respective strategy classes. The video mentions encapsulating multiple strategies within the 'calculator' class, making each strategy interchangeable and independent from others.

💡Client Program

A client program is an application that interacts with a service or another piece of software. In the Strategy Design Pattern, the client program decides which strategy (algorithm) to use at runtime. The presenter refers to the 'calculator' example, where the client program chooses whether to perform addition or subtraction.

💡Inheritance vs Composition

Inheritance is a mechanism where one class inherits the properties and behaviors of another. Composition is a design principle where objects are composed of other objects. In the Strategy Design Pattern, composition is favored because it allows algorithms to be easily interchanged without modifying the underlying classes. The presenter contrasts inheritance with the flexibility of composition, as seen in the 'calculator' class that can swap strategies at runtime.

💡Conditional Statements

A conditional statement is used in programming to make decisions based on certain conditions. In the video, the presenter discusses how using the Strategy Design Pattern can reduce the need for massive conditional statements, as different algorithms (strategies) are encapsulated in their own classes, making the code more maintainable.

💡Observer Design Pattern

The Observer Design Pattern allows an object (subject) to notify multiple observers of any state changes automatically. Although briefly mentioned, this design pattern will be covered in the next video, where it will be compared to the Strategy Design Pattern. The presenter teases this pattern as another important design principle that is widely used in software development.

Highlights

Introduction to strategy design pattern, its use, and Java code implementation.

The strategy design pattern allows the selection of algorithms at runtime.

Encapsulation of algorithms into separate classes, making their objects interchangeable.

Strategy design pattern consists of multiple related algorithms encapsulated in a context class.

Context class is not responsible for selecting the appropriate algorithm; the client passes the strategy.

Real-world example: Different transportation methods (bus, cab, bicycle) can represent various strategies.

Example of a navigation app that can have multiple route algorithms like car, bike, and walking.

Strategy design pattern prevents code duplication by keeping algorithms in separate classes.

Strategy pattern supports the open-closed principle (code open for extension but closed for modification).

Java code implementation of the strategy pattern with examples of addition, subtraction, multiplication strategies.

Test class demonstrates switching between algorithms (addition, subtraction) at runtime.

Runtime selection of algorithms like addition and subtraction in the calculator example.

Use cases for strategy pattern: when needing to switch algorithms within an object dynamically.

Benefits: Isolating the implementation details of an algorithm from the context and client classes.

Upcoming video on Observer design pattern, with Java implementation and use cases.