MainRequestHelper2.java

public MainRequestHelper(PlayerRepository playerRepository, GamesRepository gamesRepository, StatisticsProcessor statisticsProcessor) {
    this.playerRepository = playerRepository;
    this.gamesRepository = gamesRepository;
    this.statisticsProcessor = statisticsProcessor;
}

ListenableFuture<Statistics> getStatistics(String username) {
    return FluentFuture.from(playerRepository.retrieve(username))
            .transformAsync( (player) -> gamesRepository.retrieve(player.id()), directExecutor())
            .transform( (games) -> statisticsProcessor.process(games), directExecutor());
}

//RxJava version

//return playerRepository.retrieve(username)
//    .flatMap( (player) -> gamesRepository.retrieve(player.id()))
//    .map(statisticsProcessor::process);