无论如何我们都有一个空列表时如何使用空列表

Question

This question is a bit hard to explain so please look at the increasingPath function in the code here . Now assuming the path does not exist, and arraylist pointPath with 0 size is returned. However I have read that we must use Collections.emptyList, but how do I use it in this scenario, when I already have a probably empty list called pointPath ? If not to use Collections.emptyList then when to use it ?

Answer 1

I think what you're supposed to do is use Collections.EmptyList for comparisons and returning.

for example:

if (pointPath.equals(Collections.emptyList()){
    return Collections.emptyList();
}

I don't think it changes how your program will execute, but it makes the code readable and self-documenting.

Answer 2

Simply check

if (pointPath.isEmpty()){
    return Collections.emptyList();
}

The only difference from actually returning a your list that is accidentally empty is that Collections.emptyList() is immutable list. If that is not of any value to you, I'd return your real list. That way there is less code to read.