Скачать или смотреть How to Use partitioningBy and Sort Lists in Java Streams

Discover how to effectively use Java Streams to partition and sort lists of objects by multiple conditions in a seamless way.
---
This video is based on the question https://stackoverflow.com/q/72572954/ asked by the user 'Adhyatmik' ( https://stackoverflow.com/u/4469840/ ) and on the answer https://stackoverflow.com/a/72573334/ provided by the user 'Eritrean' ( https://stackoverflow.com/u/5176992/ ) 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: How to use partitioningBy and then sort resulting lists separately using Java Streams

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.
---
Mastering Java Streams: Sorting and Partitioning with Ease

In the ever-evolving world of Java programming, utilizing Java Streams to manipulate and work with collections can vastly enhance the efficiency of your code. One common task developers may face is the need to not only partition a list based on specific criteria but also sort the resulting segments separately. Today, we will explore how to achieve this with a practical example involving a collection of custom objects.

The Problem: Partitioning and Sorting Resources

Imagine you have a Resource object (as outlined below) that has three properties: level, identifier, and isEducational, with a corresponding list of these resources. You are required to sort this list primarily based on their educational status, ensuring that educational resources appear first, followed by non-educational ones, all while sorted by their level.

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

Your list of resources might look like this:

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

The desired output after sorting would be:

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

This requires that educational resources are sorted first in ascending order based on their level, followed by the non-educational resources.

The Solution: Simplifying the Approach

After attempting to use partitioningBy, it's understandable why you might find the results opposite of your desired arrangement. Fortunately, there's a more straightforward solution that involves using Comparator for sorting, allowing you to avoid unnecessary complexity. Let’s break down the steps.

Step 1: Using Comparators

Instead of relying on partitioningBy, you can simply create two comparators:

Comparator for educational status and

Comparator for level

Here's how you can achieve this using Java Streams:

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

Let's dissect this line:

Comparator.comparing(Resource::isEducational).reversed(): This part ensures that all educational resources (isEducational == true) come before non-educational ones.

thenComparing(Resource::getLevel): After categorizing educational vs. non-educational, this part sorts them by level in ascending order.

Step 2: Enhancing Code Readability

For better readability and reusability, consider defining separate Comparator variables. This is particularly useful if you want to apply the same sorting logic elsewhere in your application.

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

This separates the concerns and makes your code easier to maintain or refactor in the future.

Conclusion: Streamlining Your Code with Comparators

By leveraging Java Streams and the Comparator class, you can efficiently sort your collections of objects while achieving specific organizational goals, such as our educational vs. non-educational sorting requirement. Avoid unnecessary complexities like partitioningBy when a simpler approach can lead to clearer code without losing functionality. Try incorporating these techniques into your Java projects, and enjoy cleaner and more maintainable codebases!