null-safe mapping Comparator using default implementations

Question

Is there a build-in possibility to create a null-safe mapping comparator in Java 8 without writing a own implementation of Comparator?

When running the following code, it causes a NPE because the keyExtractor argument of Comparator.comparing() may return a null value:

public class ToSort {      private String sortBy;      public ToSort(String sortBy)     {         this.sortBy = sortBy;     }      public String getSortBy()     {         return sortBy;     }      public static void main(String[] args)     {         // mapping comparator         Comparator<ToSort> comp = Comparator.comparing(ToSort::getSortBy);                                   SortedSet<ToSort> set = new TreeSet<>(comp);         ToSort o1 = new ToSort("1");         ToSort o2 = new ToSort(null);          set.add(o1);          System.out.println(set.contains(o2)); //NPE because o2.getSortBy() == null      } } 

Exception in thread "main" java.lang.NullPointerException at java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469) at java.util.Comparator$$Lambda$2/1480010240.compare(Unknown Source) at java.util.Comparators$NullComparator.compare(Comparators.java:83) at java.util.TreeMap.getEntryUsingComparator(TreeMap.java:376) at java.util.TreeMap.getEntry(TreeMap.java:345) at java.util.TreeMap.containsKey(TreeMap.java:232) at java.util.TreeSet.contains(TreeSet.java:234) at test.ToSort.main(ToSort.java:48)

Using

Comparator<ToSort> comp = Comparator.nullsFirst(Comparator.comparing(ToSort::getSortBy)); 

does not work either as only ToSort objects that are null are treaded properly.

I know how to write my own Comparator implementation, I`m just searching a more "elegant" solution like

Comparator.comparingNullsFirst(ToSort::getSortBy) 

Answer 1

Found a possible solution:

Comparator.comparing(ToSort::getSortBy,        Comparator.nullsFirst(Comparator.naturalOrder()) )