beatbrot :
What I basically want is, that the more specialized type is inferred like in the following example:
Predicate<Object> first;
Predicate<String> second;
Predicate<String> firstOr = first.or(second);
Predicate<String> secondOr = second.or(first);
How would the method signature of or(...) look like to accomplish this?
Misha :
This can be accomplished with the following declaration of Predicate<T>::or:
default <R extends T> Predicate<R> or(Predicate<? super R> other) {
return r -> this.test(r) || other.test(r);
}
This would allow or to create a Predicate for any subtype of both Predicate types. So, for example, the following would work:
Predicate<Object> first;
Predicate<Number> second;
Predicate<Integer> firstOr = first.or(second);
Predicate<Integer> secondOr = second.or(first);