An example of method references using Java 8 Comparator static methods

MethodReferences.java

import java.util.Comparator;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.stream.Collectors;

public class MethodReferences {
  public static void main(String[] args) {
    List<String> list = new ArrayList<String>(Arrays.asList("cat", null, "foo", "aces", "bar", null, "az", null, "bc"));
    Comparator<String> cmp = Comparator.nullsFirst(Comparator.comparing((String s) -> s.length()))
      .thenComparing(String.CASE_INSENSITIVE_ORDER);
    Collections.sort(list, cmp);
    String result = list.stream().collect(Collectors.toStringJoiner(", ")).toString();
    System.out.println(result);
  }
}

results.txt

null, null, null, az, bc, bar, cat, foo, aces