public class Formatter { public static String formatAmount(double amount) { String currency = "рубль"; int rubles = (int) amount; if (rubles == 0 || rubles >= 5 && rubles <= 20 || rubles % 10 >= 5 || rubles % 10 == 0 || rubles % 100 >= 11 && rubles % 100 <= 19) { currency = "рублей"; } else if (rubles % 10 == 1) { currency = "рубль"; } else if (rubles % 10 >= 2 && rubles % 10 <= 4) { currency = "рубля"; } return String.format("%.2f %s", amount, currency); } }