Java Sonar Null Caution "null returned but Boolean expected"

Question

How I can edit this code block as a readable or logical way so that I don't get a warning from sonar? I need three result false, true or null

 public Boolean x() {
    if (...) {
        return true;
    } else if (...) {
        return false;
    } else {
        return null;
    }
}

Answer 1

Starting with Java 8 use Optional to codify TRUE, FALSE, Optional.empty. It follows the pattern "avoid returning null" and will at the same time suppress the SonarQube warning.

The code would be

public Optional<Boolean> x() { 
    if (...) { 
       return Optional.of(Boolean.TRUE); 
    } 
    else if (...) { 
       return Optional.of(Boolean.FALSE); 
    } 
    else { 
       return Optional.empty(); 
    } 
}