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Discover effective techniques for refactoring Java methods in Spring applications to eliminate duplicate code while adhering to best practices.
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Refactoring Java Methods to Eliminate Duplicate Code: A Practical Guide

In software development, duplicate code can often lead to maintenance challenges, bugs, and increased complexity. This issue is especially prominent in large applications where similar logic appears across multiple classes or methods. In this article, we'll explore a typical problem faced by many developers using Java with Spring Boot and Spring Data JPA, and provide a detailed solution for refactoring duplicate methods effectively.

The Problem: Duplicate Code in Java Methods

Consider the following scenario:
You have implemented two services, AccountRequestService and ApplicationRequestService, that share similar method implementations for paginating requests based on user status. While the logic is similar, the underlying repository interfaces differ. Here's a brief look at the methods in question:

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As you can see, both methods contain overlapping logic, leading your IDE to flag them as duplicate code. This calls for a refactoring solution to streamline these methods without losing functionality.

The Solution: Refactoring for Reusability

To solve the duplicate code issue, we can create a generic method that handles the shared functionality while accepting repository-specific query functions as parameters. Here’s how we can achieve this:

Step 1: Create a Generic Method

We will define a method called getPageable that accepts the necessary parameters, including three functional interfaces representing different query strategies.

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Step 2: Refactor the Existing Methods

Next, we refactor the original methods in AccountRequestService and ApplicationRequestService to utilize our new generic method.

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Why This Approach Works

Separation of Concerns: Each method now focuses on its core responsibility, while the getPageable method handles the common logic.

Increased Maintainability: Centralizing the logic reduces duplicate code, making future changes easier and less error-prone.

Reusability: The getPageable method can be reused elsewhere in your project if similar logic is needed.

Conclusion: Best Practices in Refactoring

When undertaking refactoring, it’s crucial to evaluate whether the shared code indicates a true similarity that should be abstracted or if it merely reflects coincidental overlap. Always strive to follow best practices such as the Single Responsibility Principle, ensuring that each module has a clear reason to change.

By applying these principles, not only do we eliminate duplicate code, but we also enhance our codebase's clarity and maintainability. As with any development task, continuous improvement and adherence to best practices will lead to a more manageable and scalable project.

Feel free to reach out if you have questions or need further assistance with refactoring practices in Java!