PremierLeagueFunctional1.java

      return leagues.stream()
		       .filter(league -> league.getLeagueName() == LeagueName.PREMIER_LEAGUE)
		       .flatMap(league ->league.getPlayers().stream())
		       .filter(player -> player.getAge() <=25)
		       .map(player ->player.getName())
		       .sorted(Comparator.naturalOrder())
		       .collect(Collectors.joining(","));