refactor: Mode

[alxkm]

• Enhanced class and method Javadocs with clearer descriptions and formatting.
• Used Map.getOrDefault() to simplify frequency counting.
• Cleaned up code style and imports for consistency.

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.60%. Comparing base (dcb02c6) to head (cd6c5b7).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6381      +/-   ##
============================================
- Coverage     74.61%   74.60%   -0.02%     
+ Complexity     5456     5453       -3     
============================================
  Files           682      682              
  Lines         19011    19009       -2     
  Branches       3671     3670       -1     
============================================
- Hits          14186    14182       -4     
- Misses         4262     4263       +1     
- Partials        563      564       +1     

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[DenizAltunkapan]

I will review this and the other PR's tomorrow step by step @alxkm

[alxkm]

@DenizAltunkapan, thank you for taking the time to review my PRs - I really appreciate it.
Just to clarify: the changes I usually submit are aimed at incremental improvements rather than major refactoring. That said, I understand that reviewing them still takes time and effort, especially with build waits and the need to merge the latest changes into new PRs.

If it makes sense to you, feel free to simply mark the PRs that have passed your review — I’d be happy to handle the merging afterward. I've used this approach in this repository before, and it worked well. Thanks again.