public List<String> nombresOrdenadosPorTamaño() {
  var lista = nombres();
  Collections.sort(lista, new Comparator<>() {
    public int compare(String s1, String s2) {
      return Integer.compare(s1.length(), s2.length());
    }
  });

  return lista;
}

Anatomía de una expresión

https://introcs.cs.princeton.edu/java/33design/images/lambda.png

Method References

(String s) -> s.length()

String::length

(String s) -> s.length()

(a, b) -> Math.max(a, b)

(a, b) -> Math.max(a, b)

Math::max

(a, b) -> Math.max(a, b)