将long转换为int，保持正/负/ 0

Question

I want to implement a java.util.Comparator with Long :

new Comparator<Long>() {
    public int compare(Long l1, Long l2) {
        // (*)
    }
}

I have a solution with operator ?: :

return l1==l2 ? 0 : (l1>l2 ? 1 : -1);

But I wonder if there is any other way to implement it.

(I was trying return (int)(l1-l2) , but it's incorrect).

Answer 1

That's easy - Long itself provides an implementation:

public int compare(Long l1, Long l2) {
    return l1.compareTo(l2);   
}

On the other hand, at that point I'm not sure why you've got a custom comparator at all...

EDIT: If you're actually comparing long values and you're using Java 1.7, you can use Long.compare(long, long) . Otherwise, go with your current implementation.

Answer 2

No, that is the only valid way to do so. This topic is already discussed a lot of times. Of course, java.lang.Long implements already a compareTo function, but it has exactly the same implementation as you have.