不确定为什么此代码无法正常运行

Question

我不确定为什么此代码不起作用。我想从while循环开始，如果满足条件，则继续进行三种可能的执行之一。

Scanner kb = new Scanner(System.in);

System.out.println("Please enter a valid product code to find out the percentage markup - DRY or FRO or HRW");
String code = kb.nextLine();   

do  { System.out.println("Please enter a valid product code to find out the percentage markup - DRY or FRO or HRW");
    code = kb.nextLine();  } 
while(code.charAt(code.length()-1)=='Y' || code.charAt(code.length()-1)=='O' || code.charAt(code.length()-1)=='W');

switch (code.charAt(code.length()-1)) {
    case 'Y':
    {
        System.out.println("The cost of Dairy is €2 and the markup is 20% please enter the number of dairy products");
        int markup = kb.nextInt();
        System.out.println("The markup for the product that you have selected is : €" +markup*0.2);
        break;
    }
    case 'O':
    {
        System.out.println("The cost of Frozen is €1 and the markup is 50% please enter the number of frozen products");
        int markup = kb.nextInt();
        System.out.println("The markup for the product that you have selected is : €" +markup*0.5);
        break;
    }
    case 'W':
    {
        System.out.println("The cost of Hardware is €5 and the markup is 25% please enter the number of harware products");
        int markup = kb.nextInt();
        System.out.println("The markup for the product that you have selected is : €" +markup*0.25);
        break;
    }
    default:
        break;
}
}
}