A function that does something with streams ... but what?

Foo.java

class Foo {
    public static <T> Function<T, Stream<T>> foo(Predicate<T> predicate) {
        return new Function<>() {
            private T previous;

            @Override
            public Stream<T> apply(T current) {
                if (predicate.test(current)) {
                    if (previous != null) {
                        T previous = this.previous;
                        this.previous = null;
                        return Stream.of(previous, current);
                    } else {
                        return Stream.of(current);
                    }
                } else {
                    previous = current;
                    return Stream.empty();
                }
            }
        };
    }
}