FloydWarshall Algorithm

[Lakuleshwari]

I’m contributing this as part of Hacktoberfest to give back to the open-source community
and improve the repository with a widely used graph algorithm.

This PR adds a clean and well-documented implementation of the Floyd-Warshall algorithm
for computing shortest distances between all pairs of vertices in a weighted graph.

Key features:

• Handles both positive and negative edge weights (no negative cycles allowed).
• Time Complexity: O(V^3), Space Complexity: O(V^2).
• Includes a self-contained Graph class and a main method for demonstration/testing.
• Fully documented with example usage to help other contributors and learners.
• Works for graphs with positive and negative edge weights (no negative cycles).
• Fully documented with usage example and test in main method.
• Follows repository conventions for package structure and code style.

I hope this addition is helpful and aligns with the project’s goals.
I would be grateful if you could review and accept my PR.
Thank you for your time and consideration!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.21%. Comparing base (f30d101) to head (ad3c8d0).

Files with missing lines	Patch %	Lines
...in/java/com/thealgorithms/graph/FloydWarshall.java	0.00%	35 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6769      +/-   ##
============================================
- Coverage     77.33%   77.21%   -0.12%     
  Complexity     6175     6175              
============================================
  Files           721      722       +1     
  Lines         20600    20635      +35     
  Branches       3994     4001       +7     
============================================
+ Hits          15931    15934       +3     
- Misses         4056     4089      +33     
+ Partials        613      612       -1     

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[vil02]

Already implemented in FloydWarshall.java.