sort method Null safety

void sort(
  1. [int compare(
    1. E a,
    2. E b

Sorts this list according to the order specified by the compare function.

The compare function must act as a Comparator.

var numbers = ['two', 'three', 'four'];
// Sort from shortest to longest.
numbers.sort((a, b) => a.length.compareTo(b.length));
print(numbers);  // [two, four, three]

The default List implementations use if compare is omitted.

List<int> nums = [13, 2, -11];
print(nums);  // [-11, 2, 13]

In that case, the elements of the list must be Comparable to each other.

A Comparator may compare objects as equal (return zero), even if they are distinct objects. The sort function is not guaranteed to be stable, so distinct objects that compare as equal may occur in any order in the result:

var numbers = ['one', 'two', 'three', 'four'];
numbers.sort((a, b) => a.length.compareTo(b.length));
print(numbers);  // [one, two, four, three] OR [two, one, four, three]


void sort([int compare(E a, E b)?]) {
  throw new UnsupportedError("Cannot sort immutable List.");