[diegourban]

Last of the three library-redesign PRs. Algorithms are moved or retyped as they are; no method bodies were rewritten.

Math

• Algebra → NumberTheory (git rename): gcd (gcdLoop, gcdRecursive), lcm, isPrime and prime factorisation.
• The new Sequences class holds fibonacci, fibonacciSimpleBinetFormula and fibonacciBinetFormula, moved unchanged together with their tests.
• Statistics now takes double[] (mode returns double). Only the types changed. Rainfall now uses Statistics.mean.
• Measurement and Geometry keep all their methods (Q10).

Property tests (jqwik)

• NumberTheory: the two gcds agree; gcd divides both numbers; lcm × gcd = a × b; the lcm of a list is a multiple of every element; isPrime agrees with trial division; prime factors multiply back to n, are all prime and come out sorted; primeFactorsSet holds the distinct factors.
• Sequences: checked exhaustively against an exact BigInteger reference over the ranges the Javadoc states (fibonacci ≤ 46, simple Binet ≤ 67, BigInteger Binet ≤ 71). All three claims hold.
• Statistics: the mean lies within [min, max]; the median is the middle of the sorted data; the mode is one of the values.
• StringUtils: isPalindrome agrees with reversing the string; mirrored strings are palindromes; shuffles are anagrams, case-insensitively; isAnagram agrees with letter counts. Inputs are ASCII letters, since both methods compare char by char.

Checked that the properties catch real bugs: breaking gcdLoop's loop condition made 4 properties fail.

Not changed, but worth knowing

• Statistics.median sorts the array it's given in place, so the caller's data gets reordered.
• Statistics.mean sums naively, so values near Double.MAX_VALUE overflow to Infinity.

Test plan

• ./mvnw verify: 581 tests, coverage floors met
• CI green

🤖 Generated with Claude Code

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 78 complexity · 0 duplication

Metric	Results
Complexity	78
Duplication	0

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AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

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[codacy-production]

Pull Request Overview

⚠️ Resolve issues before merging

Two blocking correctness gaps remain: the Binet Fibonacci implementations accept invalid negative indices, and Statistics methods fail or return NaN for empty arrays. These affect documented API behavior and should be addressed before merging. The Sequences implementation also has a precision-risk suggestion involving BigDecimal construction.

Test suggestions

• Verify both gcd implementations agree and the result divides both positive inputs.
• Verify two-value and list lcm behavior, including the gcd/lcm product invariant.
• Verify primality against trial division, including values near Integer.MAX_VALUE.
• Verify prime factors multiply to the input, are prime and sorted, and that the factor set is distinct.
• Verify all Fibonacci implementations against an exact reference over their documented ranges.
• Verify mean bounds, median ordering behavior, and mode membership for double[] data.
• Verify palindrome and anagram properties, including shuffled and case-insensitive inputs.
• Verify Statistics behavior for empty arrays, especially median and mean absolute deviation.

Prompt proposal for missing tests

Consider implementing these tests if applicable:
1. Verify Statistics behavior for empty arrays, especially median and mean absolute deviation.

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[codacy-production]

_{🟡 MEDIUM RISK}

Define and apply an explicit empty-array result before dividing by data.length.

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[codacy-production]

_{🟡 MEDIUM RISK}

Handle data.length == 0 before indexing, using the intended empty-data contract.

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[codacy-production]

_{🟡 MEDIUM RISK}

Add the same negative-index validation used by fibonacci before evaluating either Binet formula.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.09%. Comparing base (7553bca) to head (7a66409).

Additional details and impacted files

@@             Coverage Diff              @@
##             master       #9      +/-   ##
============================================
+ Coverage     92.41%   94.09%   +1.68%     
- Complexity      260      264       +4     
============================================
  Files            23       24       +1     
  Lines           593      593              
  Branches         94       94              
============================================
+ Hits            548      558      +10     
+ Misses           26       17       -9     
+ Partials         19       18       -1     

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