public class Formatter { public String formatSum(float sum) { int num = (int)sum; int penultimateNumber = num % 100 / 10; int lastNumber = num % 10; if (penultimateNumber == 1) { return "рублей"; } switch (lastNumber) { case 1: return "рубль"; case 2: case 3: case 4: return "рубля"; } return "рублей"; } }