Скачать или смотреть Sorting Objects in Java 11: Customizing Lists Based on Student Results

Learn how to sort a list of `Student` objects in Java 11 based on custom priority and roll numbers. This blog explores step-by-step solutions, code snippets, and practical examples for effective sorting in Java.
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Sorting Objects in Java 11: Customizing Lists Based on Student Results

In the world of programming, sorting lists is a common task, especially when you need to align objects according to specific criteria. If you're working on a Java 11 project that involves sorting Student objects, you may find yourself wanting to sort by specific student results and roll numbers rather than standard alphabetical order. This post addresses a common problem: How can we sort a list of Student objects according to custom priorities?

The Problem Statement

Imagine you have a list of Student objects with the attributes: name, result, and rollNo. Your goal is to sort this list based on the following criteria:

Custom Result Priority: The results should be sorted in the order - "Fail", "Pass", and then "Not available." Students with the result "Fail" should be listed first, followed by those who "Pass", and lastly, those who have "Not available".

Secondary Sorting: If multiple students share the same result, you should sort them in ascending order by their rollNo.

Here’s a sample list of Student objects:

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

Your goal is to output this list sorted according to the specified criteria.

Solution Overview

Starting with Java 8, sorting streams based on multiple fields has become straightforward. To achieve the desired sorting order, we’ll introduce a custom priority field into our Student class. This field will help define the sorting priority when there's no natural order.

Step-by-Step Guide

Modify the Student Class: Add a priority field and methods to obtain the priority based on the result.

Create a Comparator: Use the Comparator class to sort first by priority and then by roll number.

Sort Using Streams: Utilize Java Streams to sort the Student list using the defined comparator.

Step 1: Modify the Student Class

First, adjust the Student class to include a priority field and methods for determining that priority:

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

Step 2: Create a Comparator

Next, create a Comparator that first sorts by the custom priority and then by the rollNo:

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

Step 3: Sort Using Streams

You can now sort the list using Java Streams:

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

Final Output

When you execute the above code, you’ll receive the sorted output:

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

Conclusion

By following this structured approach, you can customize the sorting of Student objects in Java 11 based on non-alphabetical priorities. Implementing a priority field and utilizing Java’s powerful Streams API allows for flexible and effective sorting in your applications.

Feel free to apply these concepts to any list of objects that require custom sorting in Java!