java代码里面有一个参数出问题了，说的是amount不知道怎么了，我在下面给它了一个值还是不行，谁能帮我解答一下，帮着看看

package VendingMachine;

public class VendingMachine {
    int price = 80;
    int balance;
    int total;

    void showPrompt() {
        System.out.println("Welcome!");
    }

    void insertMoney(int amount) {
        balance = balance + amount;
    }

    void showBalance() {
        System.out.println(balance);
    }

    void getFood() {
        if(balance >= price) {
            System.out.println("Here you are.");
            balance = balance - price;
            total = total + price;
        }
    }

    public static void main(String args[]) {
        int amount = 200;
        VendingMachine vm = new VendingMachine();
        vm.showPrompt();
        vm.showBalance();
        vm.insertMoney(amount);
        vm.getFood();
    }
}