INEFFECTIVE_EQUALS_HASHCODE

Summary

• Rule ID: INEFFECTIVE_EQUALS_HASHCODE
• Name: Ineffective equals/hashCode
• Problem: Overriding only equals or only hashCode breaks collection behavior contracts.

What This Rule Reports

This rule reports classes that define one of these methods without the other: - boolean equals(Object) - int hashCode()

Java Example (reported)

class ClassA {
    @Override
    public boolean equals(Object varOne) {
        return true;
    }
}

What This Rule Does Not Report

• Classes that override both methods consistently
• Methods named equals/hashCode with non-contract signatures

Java Example (not reported)

class ClassA {
    @Override
    public boolean equals(Object varOne) {
        return true;
    }

    @Override
    public int hashCode() {
        return 1;
    }
}

Recommended Fix

If one method is overridden, override the pair with compatible semantics.

Message Shape

Findings state either: - class overrides equals(Object) but not hashCode(), or - class overrides hashCode() but not equals(Object).