When to use Comparable and Comparator

Question

I have a list of objects I need to sort on a field, say Score. Without giving much thought I wrote a new class that implements Comparator, that does the task and it works.

Now looking back at this, I am wondering if I should have instead have the my class implement Comparable instead of creating a new class that implements Comparator. The score is the only field that the objects will be ordered on.

1. What I have done acceptable as a practice?

2. Is the right approach "First have the class implement Comparable (for the natural ordering) and if an alternative field comparison is required, then create a new class that implements Comparator" ?

3. If (2) above is true, then does it mean that one should implement Comparator only after they have the class implement Comparable? (Assuming I own the original class).

Answer 1

I have been asked sorting of a definite range of numbers in better than nlogn time in one of interview. (Not using Counting sort)

Implementing Comparable interface over an object allows implicit sorting algos to use overridden compareTo method to order sort elements and that would be linear time.