I cannot seem to append my else if statement

if I try to type in the "oz" or "OZ" the else if statement doesnt seem to proceed and I do not know why. Any help would be appreciated! THANKS!!!

 Scanner input = new Scanner(System.in);
    StringBuilder sb = new StringBuilder();
    String Ma = "mass" + "MASS";
    String La = "oz" + "OZ";

        System.out.println("Hi, what are you trying to find?");
        System.out.println("mass");
        System.out.println("vol");
        System.out.println("temp");
        System.out.println("sphere");
        System.out.println("density");
        String convert = input.nextLine();

        if (Ma.contains(sb.append(convert))) {
            System.out.println("You are trying to convert mass.");
            System.out.println("Type the unit of measurement you are trying to convert to.");
            System.out.println("If you are trying to find mass type mass.");
            System.out.println("pound");
            System.out.println("ounce");
            System.out.println("ton");
            System.out.println("gram");
            System.out.println("mass");
            String mass = input.nextLine();
        }
        else if (La.contains(sb.append(convert))) {
                System.out.println("34223412351Type the number of oz.");
                double oz = input.nextDouble();
                System.out.println(oz + " oz equal to " + oz / 16 + " lb.");
                System.out.println(oz + " oz equal to " + oz / 32000 + " ton.");
                System.out.println(oz + " oz equal to " + oz * 0.02835 + " kg.");
                System.out.println(oz + " oz equal to " + oz * 28.35 + " g.");
                System.out.println(oz + " oz equal to " + oz * 2835 + " cg.");
                System.out.println(oz + " oz equal to " + oz * 28350 + " mg.");
        }
    }
}