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A comprehensive guide on implementing string sorting based on date formats and specific substrings in Java with practical code examples.
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How to Sort Strings by Date and Dynamic Substring in Java

Sorting strings in programming can often be more complex than it seems, especially when the sorting criteria involve specific embedded date formats and substrings. In this guide, we will delve into a particular challenge: sorting strings based on a date formatted as yyMMdd and a dynamic substring which can vary among 'att', 'dscl', and 'xml'.

The Problem

You have a set of filenames that include a date and certain dynamic substrings. The objective is to sort these filenames first by date, and then among the same dates, sort them by predefined priorities of dynamic substrings. Here are the filenames you need to sort:

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

Expected Sorting Logic

Primary Sorting: By date (the earlier date comes first).

Secondary Sorting: If the dates are the same, sort by the specified substring priorities:

.att files

.dscl files

Any other files (like .xml, etc.)

The expected result after sorting should look like this:

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

The Solution

To achieve the desired sorting, you can apply Java's powerful sorting functionalities along with regular expressions for date extraction. Here’s a step-by-step breakdown of the solution.

Step 1: Extract Relevant Parts of Strings

Use regular expressions to extract both the dynamic substring and the date from each filename.

Step 2: Define Substring Priorities

Create a map to keep priorities straight. You can map substrings to priority values like this:

.att → 1

.dscl → 2

Default (like .xml) → 3

Step 3: Create Comparators

You will need to create two comparators:

Date Comparator: This will compare the date part of the strings by parsing it into LocalDate.

Extension Comparator: This will utilize the priorities defined earlier to compare substrings.

Step 4: Chain the Comparators

Finally, you can chain these comparators to produce the desired sorting.

Example Implementation

Here’s a working implementation of the above logic in Java:

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

Conclusion

By following the outlined steps and utilizing the provided code, you can sort strings based on both date and dynamic substrings efficiently in Java. This approach not only improves your logical processing of strings but also demonstrates the power of the Java Collections Framework and regular expressions in handling complex data.

Feel free to experiment with different filenames and priority mappings to see how this sorting system adapts to your needs!