Streams: nullsFirst keeps a comparator safe on nulls

Comparator.nullsFirst wraps another comparator so null values sort predictably instead of throwing NullPointerException.

Code

var names = new ArrayList<>(Arrays.asList("Cara", null, "Ava", null, "Ben"));

names.sort(Comparator.nullsFirst(Comparator.naturalOrder()));
System.out.println("nullsFirst : " + names);

names.sort(Comparator.nullsLast(Comparator.naturalOrder()));
System.out.println("nullsLast  : " + names);

Output

nullsFirst : [null, null, Ava, Ben, Cara]
nullsLast  : [Ava, Ben, Cara, null, null]

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Published 2026-07-30