Is it correct to compare denominator == 0.0d to prevent division by zero?

Question

SonarQube has a rule that reports a bug in the following code, stating that " floating point numbers should not be tested for equality ". Generally this rule is justified, but in this case to me it seems to be a false positive. If it is so, I would like to flag it as such, rather than to work around it using constructs with Double.compare , checking intermediate results for +/-Infinity , NaN , or things like that.

public void f(double denominator)
{
    if (denominator == 0.0d)
        throw new IllegalArgumentException("Division by zero.");

    // code that involves division by denominator ...
}

Hence the question: Does the above code throw the IllegalArgumentException if and only if division by denominator (in expressions containing double s only) would lead to +/-Infinity or NaN intermediate values?

Answer 1

We should avoid test float for equality because of the behavior of representing decimals in binary.

The question you asked is essentially, does the above code work? Depending on how f is used, specifically if you are not explicitly passing in 0.0 as the parameter and instead doing something like f((0.4-0.1)-0.3) , it will not catch and divide by a decimal very CLOSE to 0.

PS if you want decimal precision, use BigDecimal.