SONARJAVA-6744 Implement new rule S9148: "Float.compare" or "Double.compare" should be used for floating-point comparisons

[romainbrenguier]

Detect incorrect floating-point comparisons (subtraction and relational operators on float/double) inside compareTo, Comparator.compare methods, and Comparator lambdas. Users should use Double.compare or Float.compare instead to correctly handle NaN and negative zero.

[hashicorp-vault-sonar-prod]

SONARJAVA-6744

[gitar-bot]

Code Review ✅ Approved 2 resolved / 2 findings

Implements new rule S9148 to detect incorrect floating-point comparisons inside comparison methods and lambdas, addressing null pointer exceptions on abstract methods and false positives on non-Comparator classes.

✅ 2 resolved

✅ Bug: NPE on abstract compareTo/compare methods

📄 java-checks/src/main/java/org/sonar/java/checks/FloatingPointComparisonCheck.java:46-50
isCompareToMethod/isCompareMethod match purely on name, int return type and parameter count, so an abstract int compareTo(T) or int compare(T,T) declared in an interface or abstract class also matches. MethodTree.block() is @Nullable and returns null for such methods, so methodTree.block().accept(...) throws a NullPointerException, causing the check to fail on any file containing such a declaration. Guard with if (methodTree.block() != null) before visiting.

✅ Bug: 'compare' detection does not require Comparator type

📄 java-checks/src/main/java/org/sonar/java/checks/FloatingPointComparisonCheck.java:65-69
isCompareMethod flags any method named compare that returns int and has two parameters, regardless of whether the enclosing class implements java.util.Comparator. Unrelated helper methods such as int compare(double a, double b) in an arbitrary utility class will produce issues even though they are not part of a Comparator contract, leading to false positives. Consider verifying the enclosing class is a subtype of java.util.Comparator (mirroring the lambda handling) or that the method is an override of Comparator.compare.

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[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
98.7% Coverage on New Code
0.0% Duplication on New Code

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