private void massConversionsMenu() throws InterruptedException {

    System.out.println();
    println("Choose a conversion or enter any integer to go back: ");
    println("0: Grams to milligrams");
    println("1: Milligrams to grams");
    println("2: Grams to kilograms");
    println("3: Kilograms to grams");
    println("4: amu to grams");
    println("5: Grams to amu");

    switch (input.nextInt()) {

      case 0:
        // Grams to milligrams
        amount();
        double grams = input.nextDouble();
        println(Conversions.gramsToMilligrams(grams) + " mg");
        break;

      case 1:
        // Milligrams to grams
        amount();
        double milligrams = input.nextDouble();
        println(Conversions.milligramsToGrams(milligrams) + " g");
        break;

      case 2:
        // Grams to kilograms
        amount();
        double grams1 = input.nextDouble();
        println(Conversions.gramsToKilograms(grams1) + " kg");
        break;

      case 3:
        // Kilograms to grams
        amount();
        double kilograms = input.nextDouble();
        println(Conversions.kilogramsToGrams(kilograms) + " g");
        break;

      case 4:
        // amus to grams
        amount();
        double amus = input.nextDouble();
        println(Conversions.amuToGram(amus) + " g");
        break;

      case 5:
        // Grams to amus
        amount();
        double grams2 = input.nextDouble();
        println(Conversions.gramToAmu(grams2) + " amu");

      default:
        // Go back to conversions menu
        conversionsMenu();
    }

  }