Sort an ArrayList of Strings that are numbers

Question

What is the fastest way to sort an ArrayList (in descending/ascending manner) that contains numbers, eg: { \"12\", \"3.5\", \"188\", \"33.03

Answer 1

If you are using Java 8, you can use Comparator.comparing(Double::parseDouble) to quickly create a comparator using parseDouble. This should (see below) call the function just once for each entry, and not once for each pair.

List list = Arrays.asList( "12", "3.5", "188", "33.03" );
list.sort(Comparator.comparing(Double::parseDouble));
System.out.println(list);

Output:

[3.5, 12, 33.03, 188]

Update: Well, I thought this would call the comparator function just once for each element, like using a key-function in Python, but after a quick test using a function increasing a counter each time it is called, the function is called just as often as using an old-style "pair"-comparator. Still, a bit shorter...