Скачать или смотреть Resolving Comparator Error java.lang.IllegalArgumentException When Sorting by Set Bits in Java

Learn how to fix the `Comparator Error java.lang.IllegalArgumentException` in Java when attempting to sort an array based on the count of set bits. This guide provides clear solutions and best practices for using comparators effectively.
---
This video is based on the question https://stackoverflow.com/q/68057480/ asked by the user 'Sahil Kumar' ( https://stackoverflow.com/u/16274322/ ) and on the answer https://stackoverflow.com/a/68057542/ provided by the user 'Unmitigated' ( https://stackoverflow.com/u/9513184/ ) 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: Comparator Error java.lang.IllegalArgumentException

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.
---
Understanding and Fixing the Comparator Error in Java

When working with Java, you might encounter various exceptions that can derail your progress and create unnecessary frustration. One such error is the IllegalArgumentException often thrown by the Comparator. In this post, we will discuss the common pitfalls when using a custom comparator and explore how to sort an array based on the count of set bits without running into errors.

The Problem: What Is the IllegalArgumentException?

The Scenario

You may have a requirement to sort an array of integers according to the number of set bits (bits with a value of 1) in their binary representation. The code snippet below illustrates a common approach to sorting using a lambda comparator:

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

The Exception

Upon execution, this code might lead to the following exception:

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

This error indicates that the custom comparator logic is inconsistent and not adhering to the general contract of comparison methods.

The Solution: Correcting the Comparator

Understanding the Problem with the Existing Comparator

The primary issue in the provided comparator is that it does not return 0 when the two elements being compared are considered equal. The contract for comparators states that if compare(a, b) returns 0, then both a and b are deemed equal. Failing to comply with this can lead to unpredictable sorting results and, consequently, exceptions like the one you've encountered.

A Better Approach: Using Comparator.comparingInt

To rectify this issue, we can utilize the built-in Comparator.comparingInt method. This approach simplifies the expression and ensures that the correct comparison contract is maintained. Here is how you can implement it:

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

Why This Works

Comparator.comparingInt: This method takes a function that extracts an int value from the elements being compared, in this case, the count of set bits.

.reversed(): This method flips the order to sort in descending rather than ascending, which suits your requirement of sorting by set bits.

Benefits of This Approach

Simplicity: The comparingInt method is concise and reduces the chances of logic errors.

Consistency: The method adheres to the necessary comparison contract, preventing exceptions.

Conclusion

In summary, encountering a Comparator Error java.lang.IllegalArgumentException when sorting by set bits in Java can be tackled effectively by understanding the requirements of the comparator contract. By utilizing the Comparator.comparingInt method, you create a robust and error-free sorting mechanism that maintains clarity and enhances code readability.

For any further queries or clarifications regarding Java comparators or sorting techniques, feel free to reach out!