SortedSetComparatorのComparatorを作る

IterableComparator.java

public class IterableComparator {
	public static <T> Comparator<Iterable<T>> iterableComparator(Comparator<? super T> elementComparator) {
		return (l1, l2) -> {
			Iterator<T> i1 = l1.iterator();
			Iterator<T> i2 = l2.iterator();
			while(i1.hasNext() && i2.hasNext()) {
				T t1 = i1.next();
				T t2 = i2.next();
				int c = elementComparator.compare(t1, t2);
				if(c != 0) {
					return c;
				}
			}
			if(i1.hasNext()) {
				return 1;
			}
			if(i2.hasNext()) {
				return -1;
			}
			return 0;
		};
	}
	private static String cmpToString(int i) {
		return i < 0 ? "<" :
				i > 0 ? ">" :
				"=";
	}
	public static void main(String[] args) {
		SortedSet<Integer> s1 = new TreeSet<>(Set.of(1, 2, 4));
		SortedSet<Integer> s2 = new TreeSet<>(Set.of(1, 3, 4));
		SortedSet<Integer> s3 = new TreeSet<>(Set.of(1, 2));

		Comparator<Iterable<Integer>> cmp = iterableComparator(Comparator.naturalOrder());

		System.out.printf("s1 %s s1%n", cmpToString(cmp.compare(s1, s1)));
		System.out.printf("s1 %s s2%n", cmpToString(cmp.compare(s1, s2)));
		System.out.printf("s1 %s s3%n", cmpToString(cmp.compare(s1, s3)));
	}
}