PremierLeagueImperative.java

List<Player> validPlayers = new ArrayList<>();
FootballLeague premierLeague = null;
for(FootballLeague league:leagues)
{
	if(league.getLeagueName() == LeagueName.PREMIER_LEAGUE )
	{
		premierLeague = league;
		break;
	}
}
		
if(null != premierLeague)
{
	List<Player> players = premierLeague.getPlayers();
	for(Player player: players)
	{
		if(player.getAge() <= 25)
		{
		 validPlayers.add(player);
		}
	}
}
		
  Collections.sort(validPlayers, new Comparator<Player>() {
  @Override
	public int compare(Player p1, Player p2 ) {
			return p1.getName().compareTo(p2.getName());
		}
	});
		
	StringBuilder builder = new StringBuilder();
	for(Player player : validPlayers)
	{
		builder.append( player.getName()+ ",");	
	}
		
	return builder.substring(0,builder.length()-1);