@SupportedAnnotationTypes("*")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class AllProcessor extends AbstractProcessor {
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {

        Set<? extends Element> rootElements = roundEnv.getRootElements();
        for (TypeElement type : ElementFilter.typesIn(rootElements)) {
            checkConstructors(type);
        }
        return false;
    }

    private void checkConstructors(TypeElement type) {
        boolean pubNonArgConstr = false;
        for (ExecutableElement cons : ElementFilter.constructorsIn(type.getEnclosedElements())) {
            boolean publicConstructor = cons.getModifiers().contains(Modifier.PUBLIC);
            String docComment = processingEnv.getElementUtils().getDocComment(cons);
            if (publicConstructor && docComment == null) {
                processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, "public constructor must has JavaDoc: ", cons);
            }
            if (cons.getParameters().isEmpty() && publicConstructor) {
                pubNonArgConstr = true;
            }
        }
        if (!pubNonArgConstr) {
            processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, "is missing a public default constructor: ", type);
        }
    }
}