public class Formatter { public String rubCoast(double coast) { String rubString; int lastDigit = (int) Math.floor(coast) % 10; int secondToLastDigit = ((int) Math.floor(coast) / 10) % 10; if (secondToLastDigit == 1) { rubString = "рублей"; } else { rubString = switch (lastDigit) { case 1 -> "рубль"; case 2, 3, 4 -> "рубля"; default -> "рублей"; }; } return String.format("%.2f %s.", coast, rubString); } }