Yishai Yishai - 7 months ago 33
Java Question

Does a natural comparator exist in the standard api?

I need a comparator as part of a strategy pattern that can either use the natural ordering of the objects or some custom ordering. For the natural ordering case, I wrote a simple comparator:

private static class NaturalComparator<T extends Comparable<? super T>> implements Comparator<T> {
@Override
public int compare(T o1, T o2) {
return o1.compareTo(o2);
}
}


Seems simple enough, but I was wondering if anyone knew of one in the standard API. I looked at TreeMap, and it does it without such a class, so when that code was written, the apparent answer would be no, but perhaps it was added later.

Answer

Added to Comparator in Java 8:

static <T extends Comparable<? super T>> Comparator<T> naturalOrder()

Use it like this, for example:

Comparator<Double> natural = Comparator.<Double>naturalOrder();
return natural.compare(1.0, 1.1));