Скачать или смотреть How to Efficiently Run Static Scope for Every Subclass in Java

Discover how to effectively manage static scope in Java subclasses. Learn a simple solution to print subclass names on first instance creation.
---
This video is based on the question https://stackoverflow.com/q/64220996/ asked by the user 'Lupidon' ( https://stackoverflow.com/u/11960656/ ) and on the answer https://stackoverflow.com/a/64221625/ provided by the user 'Andreas' ( https://stackoverflow.com/u/5221149/ ) 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 there a way to run static scope for every subclass once?

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

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Efficiently Run Static Scope for Every Subclass in Java: A Comprehensive Guide

In the world of Java, working with abstract classes and their subclasses can sometimes lead to challenges, particularly concerning static scopes. Developers often find themselves needing a way to execute specific code when a subclass is instantiated for the first time, yet only on that initial call. In this guide, we'll explore an elegant solution to achieve this functionality without compromising your code's organization or readability.

The Problem: Managing Static Scope in Subclasses

Consider a scenario in which you have an abstract class designed to be inherited by various subclasses. You want to ensure that when a subclass is instantiated for the first time, certain static code (like printing the subclass name) is executed. However, you don't want this static code to run every time an instance of the subclass is created after that first instantiation.

For example, given the following abstract base class:

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

When you extend this class, the static block runs every time. This results in unnecessary duplicates of the output. Here's what you might intend to see for the first run of a subclass like SubClass:

"hello"

"subclassInfo"

But for subsequent runs of the same subclass, you want only "hello".

The Solution: Using A Static Map to Track Subclass Instantiations

To achieve our goal, we can use a static Map that tracks whether a subclass has been instantiated before. This approach leverages the benefits of a ConcurrentHashMap from the Java Collections Framework for thread safety and efficiency. Here’s how you can implement this:

Step-by-Step Implementation

Define the Base Class: Set up the base class with a static map that checks for previously instantiated subclasses.

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

Define Subclasses: Create any number of subclasses that extend Base. When instantiated, they will automatically check against the map.

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

Test the Implementation: In a test class, instantiate the subclasses multiple times to see different output.

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

Expected Output

When the above code runs, you should see output indicating the new subclass being instantiated only when it is created for the first time:

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

Conclusion

This approach not only resolves the issue of redundant static scope execution but does so in a clear and efficient manner. Utilizing a static map inside your base class ensures that any subclasses will print their instantiation message only when they are first created.

By applying this technique, Java developers can maintain clean and manageable code while enhancing readability and functionality.

Implementing these best practices can greatly improve your Java programming experience, particularly when working with complex class hierarchies.

Feel free to share your thoughts or any questions you might have about managing static scopes in Java in the comments below!