接受多个谓词作为方法的参数

Question

I'm pretty new to Java and following a course to understand it better. In the Test code below we are supposed to be able to create a method that accepts multiple Predicate . I can't seem to get it right. Collections seem logical but they can't be used. so I thought Predicate<T>[] predicates would suffice. But no success there.

public class Utils {
//    public static <T> Predicate<T> anyPassPredicate(Predicate<T>[] predicates) {
    public static <T> Predicate<T> anyPassPredicate(Collection<Predicate<T>> predicates) {
        Predicate<T> pred = predicates.stream().reduce(Predicate::or).orElse(x->false);;
        return pred;
    }

    public static <T> T firstAnyMatch(List<T> list, Predicate<T> predicate) {
        for (T element : list) {
            if (predicate.test(element)) {
                return element;
            }
        }
        return null;
    }
}

Test code

public class Test {
    public static void main(String[] args) {
        List<String> words = Arrays.asList("Jan", "Jos", "Anna", "Pieter", "Johan");
        Predicate<String> anyMatch = Utils.anyPassPredicate(s -> s.contains("o"), s -> s.length() > 5);
        Utils.firstAnyMatch(words, anyMatch);
    }
}

How is it possible to accept multiple Predicate as argument to the method?

Answer 1

In order for a method to accept an unspecified number of arguments of the same type, you need to use varargs , which is specified by an ellipsis

static <T> Predicate<T> anyPassPredicate(Predicate<T>... predicates) {
    return Arrays.stream(predicates)
         .reduce(Predicate::or)
         .orElse(x->false);
}