Java by Comparison: Thoughts on "Avoid Negations" (page 4)

TL;DR: words that incorporate negation are acceptable, eg. independent, asymmetric, nondeterministic.

An example in the book is to rename isInorganic() to isOrganic(), but I think this is too mechanical and goes too far. The field of inorganic chemistry thinks of itself positively, and its domain vocabulary includes the word. More important than recognizing words that contain negation is to respect the domain terminology. Also it is more important to consider the typical usage in code. For example, when following the “Fail Fast” pattern, we expect something like this pseudocode: if isInvalid(arg) { throw new exception } I think that the authors might recognize this as they use isUnknown(), a positive statement of negation, is a later example.

I agree it is generally better to avoid negative logic, and that coders should know De Morgan’s laws (page 7), but I find it ironic that turning this

boolean isValid() {
    return missions >= 0 && name != null && !name.trim().isEmpty();
}

into

boolean isValid() {
    boolean isValidMissions = missions >= 0;
    boolean isValidName = name != null && !name.trim().isEmpty();
    return isValidMissions && isValidName;
}

is considered better than this

boolean isInvalid() {
    return missions < 0 || name == null || name.trim().isEmpty();
}

(which can be easily lambda-ized to boot).