import java.util.stream.*;
import java.util.*;

class Ideone {
  public static void main (String[] args) {
    Map<String, Stream<String>> map = new HashMap<>();
    map.put("A", Stream.of("B", "C", " D "));
    map.put("B", Stream.of("kas", "B", "c ", "dddd"));
    listN(map).forEach(System.out::println);
 }

public static Stream<String> listN(Map<String, Stream<String>> map) {
    return map.values().stream()
      .flatMap(s -> s)
      .filter(s -> s != null && !s.isEmpty())
      .map(String::trim)
      .map(String::toLowerCase)
      .map(s -> s.substring(0, 1).toUpperCase() + s.substring(1))
      .distinct()
      .sorted();
}
}