How to simplify comparing?-CodePudding

I do have list like this:

List<Integer> list = new ArrayList<>();
    list.add(24);
    list.add(12);
    list.add(0);
    list.add(36);
    list.add(1);
    list.add(99);

I want to sort it ascendig, but 0 has to always be on the last one. Is there any way to simplify it?

   List<Integer> collect = list.stream()
            .sorted((a,b) -> b.compareTo(a))
            .sorted((a, b) -> Integer.valueOf(0).equals(a) ? 1 : -1)
            .collect(Collectors.toList());

CodePudding user response：

List<Integer> list = List.of(24, 12, 0, 36, 1, 99);
List<Integer> sorted = list.stream()
.sorted(Comparator.comparingInt(a -> a == 0 ? Integer.MAX_VALUE : a))
.toList();
System.out.println(sorted);

Seems to work; prints [1, 12, 24, 36, 99, 0].

The one downside is that it won't do the right thing if literally the maximum integer value (which is 2147483647) is in your list, in which case it'll sort the 0s amongst them instead of after them. If that is a problem, nothing is going to look significantly shorter than what you did.

NB: Your code appears to sort descending. In which case the 0 would already sort at the end unless you have negative numbers. If that's what you want and 'ascending' was a typo, you'd have to use MIN_VALUE instead, and reverse the comparator (tack .reverse() t the end).

CodePudding user response：

You can process in the same sorted:

List<Integer> collect = list.stream()
                        .sorted((o1, o2) -> o1 == 0 ? 1 : (o2 == 0 ? -1 : o1.compareTo(o2)))
                        .collect(Collectors.toList());

CodePudding user response：

May be introducing variables for the comparators and comparing the boolean if an int equals to zero might simplify or at least make it readable

Comparator<Integer> natural  = Comparator.naturalOrder();
Comparator<Integer> zeroLast = Comparator.comparing(i -> i.equals(0));

List<Integer> collect = list.stream()
                            .sorted(natural)
                            .sorted(zeroLast)
                            .collect(Collectors.toList());

CodePudding user response：

You can use 1 ternary operator in the same sort function. Check the following

 List<Integer> collect = list.stream()
            .sorted((o1, o2) -> (o1 == 0 || o2 == 0) ? -Integer.compare(Math.abs(o1), Math.abs(o2)) : o1.compareTo(o2))
            .collect(Collectors.toList());