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 74.64%. Comparing base (ef93cc1) to head (b7f22b8).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6381   +/-   ##
=========================================
  Coverage     74.64%   74.64%           
+ Complexity     5445     5443    -2     
=========================================
  Files           682      682           
  Lines         19000    18998    -2     
  Branches       3668     3667    -1     
=========================================
  Hits          14182    14182           
+ Misses         4260     4259    -1     
+ Partials        558      557    -1     

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