Is there a way to use Eclipse external annotations on a class' generic parameters?

Question

I would like to annotate Vaadin's HasComponents class, which extends Iterable. I can annotate the iterator()-Method like this:

class com/vaadin/ui/HasComponents
iterator
 ()Ljava/util/Iterator<Lcom/vaadin/ui/Component;>;
 ()L1java/util/Iterator<L1com/vaadin/ui/Component;>;

so that I can iterate with a classic for-loop

for (Iterator<Component> it = content.iterator(); it.hasNext();) {
  Component c = it.next();
  doSmoething(c);
}

but when I try a foreach-loop like

for(Component c : content) {
  doSomething(c);
}

I get a warning from Eclipse:

Null type safety (type annotations): The expression of type 'Component' needs unchecked conversion to conform to '@NonNull Component'

presumably because it should be

HasComponents extends Component, Iterable<@NonNull Component> 

Is there any way to add this annotation via external annotations or is there another way?

Answer 1

如果您的最终目标是简化循环，并且您正在使用Java 8或更高版本，则可以通过Streams和Lambda通过以下方式将forEach（..）与HasComponents结合使用：

layout.forEach(component -> { ... do something with component ... });