comparator with null values

Question

We have some code which sorts a list of addresses based on the distance between their coordinates. this is done through collections.sort with a custom comparator.

How

Answer 1

If you are using Java 8, you have 2 new static methods in the Comparator class, which come in handy:

public static  Comparator nullsFirst(Comparator comparator)
public static  Comparator nullsLast(Comparator comparator)

The comparison will be null safe and you can choose where to place the null values in the sorted sequence.

The following example:

List monkeyBusiness = Arrays.asList("Chimp", "eat", "sleep", "", null, "banana",
            "throw banana peel", null, "smile", "run");
Comparator comparator = (a, b) -> a.compareTo(b);
monkeyBusiness.stream().sorted(Comparator.nullsFirst(comparator))
            .forEach(x -> System.out.print("[" + x + "] "));

will print: [null] [null] [] [Chimp] [banana] [eat] [run] [sleep] [smile] [throw banana peel]