Floating point values should not be compared with relational operators in comparison methods JAVA-W1032

A comparison method (such as compareTo, equals or compare) seems to be using relational operators (<, >, et al) to compare floating point numbers. The behavior of these operators deviates from the method contracts of Float.compare and Double.compare, which may cause inconsistent behavior with standard library collections, and possibly other container APIs as well.

In Java, the way relational operators (<, >, et al) evaluate floating point values differs from how Float.compare() or Double.compare() are implemented.

From the JavaDoc for Float.compare(float, float):

There are two ways in which comparisons performed by this method differ from those performed by the Java language numerical comparison operators ( <, <=, ==, >=, >) when applied to primitive float values: * Float.NaN is considered by this method to be equal to itself and greater than all other float values (including Float.POSITIVE_INFINITY). * 0.0f is considered by this method to be greater than -0.0f.

Similar differences exist for Double, and these differences also apply to the equals and compare methods of these types.

Bad Practice

private double someDoubleField;

@Override
int compareTo(T other) {
    if (other.someDoubleField == this.someDoubleField) {
        // ...
    }
}

Recommended

Use the relevant compareTo or compare method on the floating point values to be compared instead.

@Override
int compareTo(T other) {
    if (Double.compare(this.someDoubleField, other.someDoubleField)) {
        // ...
    }
}

Exceptions

This issue is only reported when such comparisons are found within comparison methods such as compareTo and equals.