interface Message<T, L> {
}
interface Foo<T> {
void frob(Message<T, Foo<?>> message);
}
class AuxiliaryFoo implements Foo<Integer> {
@Override
public void frob(Message<Integer, Foo<?>> message) { }
}
class MainFoo implements Foo<Object> {
@Override
public void frob(Message<Object, Foo<?>> message) {
new AuxiliaryFoo().frob(new Message<Integer, MainFoo>() {});
}
}
Java 编译器告诉我actual argument < anonymous Message< Integer, MainFoo >> cannot be converted to Message< Integer, Foo< ?>> by method invocation conversion
.
为什么?
什么可以转换为 Message< Integer, Foo< ?>> ?