Add tests for NodeStack and rework

[lorduke22]

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• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] 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 :white_check_mark:

Project coverage is 72.36%. Comparing base (a163816) to head (f2fef25).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6009      +/-   ##
============================================
- Coverage     72.37%   72.36%   -0.01%     
+ Complexity     4981     4979       -2     
============================================
  Files           652      652              
  Lines         17569    17564       -5     
  Branches       3385     3384       -1     
============================================
- Hits          12716    12711       -5     
  Misses         4373     4373              
  Partials        480      480              

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[lorduke22]

I cannot solve this PR because during a CI/CD pipeline run with Infer, a potential Null Dereference was detected in the BinaryTreeTest class. The analysis flagged the following line as a potential issue:

src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java:38: error: Null Dereference(NULLPTR_DEREFERENCE) BinaryTree$Node BinaryTree.getRoot() could be null (from the call to BinaryTree() on line 28) and is dereferenced.

To solve the build problem, if I wish, I can apply a temporary fix to prevent the test from failing on the BinaryTreeTest class (e.g., by adding a null check in getRoot())

@siriak Let me know how to proceed

[siriak]

Hmm, that's odd. Could you try to fix the issue here or in a separate PR?

[Chiefpatwal]

I cannot solve this PR because during a CI/CD pipeline run with Infer, a potential Null Dereference was detected in the BinaryTreeTest class. The analysis flagged the following line as a potential issue:

src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java:38: error: Null Dereference(NULLPTR_DEREFERENCE) BinaryTree$Node BinaryTree.getRoot() could be null (from the call to BinaryTree() on line 28) and is dereferenced.

To solve the build problem, if I wish, I can apply a temporary fix to prevent the test from failing on the BinaryTreeTest class (e.g., by adding a null check in getRoot())

@siriak Let me know how to proceed

Hey @lorduke22, I’m facing the same conflict issue due to the failing Infer run check. I’m stuck and could use some guidance if you have any insights on resolving it.

[lorduke22]

@siriak I should have solved the problem in this PR. Hi @Chiefpatwal, the problem lies in the BinaryTreeTest class I see the getRoot() method may return null if the root node has been removed and there are no more nodes in the tree. This is why Infer reports a potential NullPointerException when attempting to access the date field in t.getRoot().data. To resolve the error, I added a null check on getRoot() in test2.

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