Скачать или смотреть How to Sort a String Array by Employee ID Number in Java

Learn how to effectively sort a string array based on employee ID numbers using custom comparators in Java.
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This video is based on the question https://stackoverflow.com/q/66009654/ asked by the user 'Loweljay Alburo' ( https://stackoverflow.com/u/7084866/ ) and on the answer https://stackoverflow.com/a/66009787/ provided by the user 'Andy Turner' ( https://stackoverflow.com/u/3788176/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Sort a String Array by Employee ID Number in Java

Sorting data is a common task in programming, especially when dealing with databases or lists of entities like employees. In this guide, we’ll address a typical problem: sorting an array of strings that represent employee details by their ID numbers instead of their names.

The Problem: Incorrect Sorting

You may encounter a situation where you have a list of employee details like this:

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

When sorting this list using the default Collections.sort() method, the output you get may seem unexpected:

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

As you can see, the list is sorted by names instead of the ID numbers, which is not what we want. The desired outcome would be:

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

So how can we accomplish this? Let's dive into the solution!

The Solution: Custom Comparator

To sort the string array based on the employee ID numbers, we can implement a custom comparator. This comparator will focus on extracting the ID numbers from each string, allowing us to sort based on this value instead of the entire string.

Step-by-Step Guide

Define the Comparator
We will create a comparator that extracts the ID from each string. The ID is located between the first and second commas in each line.

Use Collections.sort
Instead of directly applying Collections.sort(), we will pass our custom comparator that we created in the previous step.

Implementing the Code

Here’s how you can implement the above steps in Java:

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

Breakdown of the Code

Reading the File: We read lines from a file named Database.txt and store them in an ArrayList.

Custom Comparator:

We utilize Comparator.comparingInt() to create a comparator that reads the substring between the first and second commas.

The extracted substring is parsed into an integer for sorting purposes.

Sorting the List: The sort method is called with our custom comparator, ensuring that the list is sorted by employee ID numbers.

Writing to Output: Finally, we write the sorted list to a new file, final.txt.

Conclusion

Sorting an array of strings by an ID number rather than by names requires a bit of customization in our approach. By using a custom comparator, we can precisely control how our data is ordered.

So the next time you need to sort strings based on a specific part of the content, remember that a custom comparator is your best friend!



Happy coding! If you have any questions or comments, feel free to leave them below!