Скачать или смотреть How to Sort a List of Custom Java Objects with a Comparator

Learn how to sort a list of custom objects in Java using a `Comparator` to order them based on specific criteria like names starting with alphabets, numbers, or special characters.
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This video is based on the question https://stackoverflow.com/q/62453526/ asked by the user 'tharunya' ( https://stackoverflow.com/u/10538742/ ) and on the answer https://stackoverflow.com/a/62455775/ provided by the user 'codeSeeker' ( https://stackoverflow.com/u/11240620/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Sorting with a Comparator in Java: A Guide

Sorting data is a common task in programming, and Java provides powerful tools for this. If you have a custom class and you want to sort a list of its objects based on specific criteria, you'll often use a Comparator. In this guide, we'll explore how to sort a list of Details objects based on the name's starting character—whether it is an alphabet, a number, or a special character.

The Challenge

Imagine you have a list of custom objects defined in a Details class, and you need to sort them in the following order:

Names starting with alphabets

Names starting with numbers

Names starting with special characters

Example of the Details Class

Here's a simple representation of what the Details class looks like:

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Suppose we have multiple Details objects, and we want to achieve the following sorted result based on their name attribute:

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The Solution

To tackle this problem, we'll utilize Java's Stream API and Comparator. Here's a step-by-step breakdown of how to implement the sorting logic accurately.

Step 1: Define the Priority Method

First, we need a method to assign priority based on the character that each name starts with. This method will help categorize the names into the three sorting groups listed earlier.

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Returns 1 if the first character is an alphabet.

Returns 2 if the first character is a digit.

Returns 3 if the first character is a special character.

Step 2: Use the Comparator with Streams

Next, we can use a Comparator combined with Java Streams to sort our list of Details objects. Here's how the core sorting operation looks:

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Streams: We convert our list of objects to a stream for processing.

Comparator: The sorting is done based on the priority determined by the priority method, followed by natural sorting of names.

Collecting: Finally, we collect the sorted stream back into a list.

Complete Code Example

Here’s the complete code with both the Details class and the sorting logic:

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

Conclusion

Sorting custom objects based on specific criteria can be accomplished efficiently in Java using the Comparator and Streams. By defining a clear priority for sorting and leveraging Java's functional programming features, you enhance the readability and maintainability of your code.

Happy coding!