NeonNumber algorithm in maths package

[AshishKumar1297]

Added NeonNumber algorithm that checks if a
number is a Neon Number.
Example: 9 → 9²=81 → 8+1=9 ✓

• I have read CONTRIBUTING.md
• This pull request is my own work
• All filenames are in PascalCase
• All functions and variable names follow Java naming conventions
• All new algorithms have a URL in their comments
• All new algorithms include a corresponding test class

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.54%. Comparing base (e814d97) to head (5691cb7).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7420   +/-   ##
=========================================
  Coverage     79.53%   79.54%           
- Complexity     7177     7180    +3     
=========================================
  Files           798      799    +1     
  Lines         23474    23481    +7     
  Branches       4617     4619    +2     
=========================================
+ Hits          18671    18678    +7     
  Misses         4055     4055           
  Partials        748      748           

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[prashantpiyush1111]

Overall structure is good — final class, private constructor,
and JavaDoc are all in place.

However, there are a few issues that need to be fixed
before merging:

1. Integer overflow in isNeon() method
2. No handling for negative inputs
3. isNeon(0) works by coincidence, not by logic
4. Missing edge case tests

Please address the inline comments.

[prashantpiyush1111]

Integer overflow risk! For large inputs (e.g. number = 50000),
number * number exceeds Integer.MAX_VALUE and gives wrong result.

Fix:
long square = (long) number * number;

[prashantpiyush1111]

No validation for negative numbers. isNeon(-5) won't crash
but behavior is unintended.

Fix: Add at the start of method:
if (number < 0) {
throw new IllegalArgumentException("Input must be non-negative");
}

[prashantpiyush1111]

When number = 0, temp = 0, so this loop never runs.
isNeon(0) returns true only by coincidence.

Fix:
if (number == 0) return true;

[prashantpiyush1111]

assertTrue(NeonNumber.isNeon(0)) passes but for wrong reason —
loop never executes for 0. Consider adding explicit test
that verifies the logic, not just the output.

[prashantpiyush1111]

Missing edge case tests:

1. Negative input:
   assertThrows(IllegalArgumentException.class,
   () -> NeonNumber.isNeon(-1));

2. Large number to catch overflow:
   assertFalse(NeonNumber.isNeon(50000));

[prashantpiyush1111]

Comment box mein ye likho:

Please address the inline comments
before this can be merged:

1. Integer overflow: use
   long square = (long) number * number

2. Add negative input validation

3. Handle isNeon(0) explicitly

4. Add missing edge case tests