Скачать или смотреть How to Compare Nested IDs to Get the Lower Value in Java Using Functional Programming

Learn how to efficiently compare nested alphanumeric IDs in Java using functional programming techniques to find the minimal ID value.
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Comparing Two IDs to Get the Lower Value in Java

When working with collections of objects in Java, particularly with nested attributes, you may encounter scenarios where you need to compare values to determine which is "lower." A common situation arises when dealing with alphanumeric IDs, which can be a challenge since they all have different characters and lengths. In this guide, we will specifically look at how to compare two IDs represented as nested properties within your objects, using Java's Functional Programming features.

The Problem at Hand

Imagine you have a collection of SupplyDto objects, each containing a SupplierProviderDto with an ID and NIF (tax identification number). Your goal is to find the lowest NIF among these providers. The IDs you're comparing are alphanumeric, such as "836778436K" and "K8474874".

Given this requirement, you might be unsure of how to implement the correct comparison using the min function in a stream. The challenge is understanding which lambda function to use in order to achieve this comparison effectively.

Understanding the Data Structure

Before we dive into the solution, let’s clarify the structure of the SupplyDto class, which is crucial to your setup:

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

Key Attributes:

nif: This is the attribute we need to compare.

provider: This is the nested object containing the nif.

The Solution

To achieve your goal of finding the minimal NIF, you can utilize Java's stream capabilities combined with a functional programming approach. Here are two solutions you might use, depending on your needs.

1. Finding the Minimal NIF

If you simply want to identify the minimal NIF from the list of providers, you can use the following approach:

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

Explanation of the Code:

stream(): Converts the collection into a stream for processing.

map(dto - dto.provider.nif): Extracts the NIF from each SupplyDto object.

min(String::compareTo): Compares the NIFs as strings and finds the minimum one.

orElse("No minimal nif found"): Provides a default message if no minimum value is found.

2. Getting the ID of the DTO with Minimal NIF

If you wish to obtain the ID corresponding to the minimal NIF, the following snippet will be your go-to solution:

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

Code Breakdown:

min(Comparator.comparing(dto - dto.provider.nif)): Here, a comparator is used to determine the minimal NIF based on the provider's NIF of each SupplyDto.

map(dto - dto.provider.id): Extracts the ID associated with the DTO containing the minimal NIF.

orElse("No ID for minimal nif found"): Outputs a friendly message if there are no results.

Conclusion

By leveraging Java's functional programming capabilities, you can efficiently compare nested IDs within your data structures, making your code cleaner and more manageable. Whether you're after the minimal value itself or the associated ID, these techniques can help you achieve your goals effectively.

Key Takeaway

Using functional programming with streams can simplify the process of comparing and extracting values from complex nested objects in Java. So the next time you face a similar scenario, you’re equipped with the tools to tackle it efficiently!