java - 使用 int 变量控制 Do...While() 循环不起作用

Question

编辑:问题是我没有在其外部声明变量

我的循环无法将 int 解析为变量。

不能尝试其他类型的变量，这必须是整数。

        do {
            System.out.println("Would you like to add any snacks? ");
            System.out.println("1: ($5) Large Popcorn");
            System.out.println("2: ($0) Nothing Else");
            int snackChoice = input.nextInt();

            System.out.println("How many of option " + snackChoice + " would you like? ");
            System.out.println("1: One");
            System.out.println("2: Two");
            System.out.println("3: Three");
            System.out.println("4: Four");
            System.out.println("5: Five");
            int snackAmount = input.nextInt();

            switch (snackChoice) { 
            case 1: 
                cost = cost + 5 * snackAmount;
                System.out.println("Your total before tax will be: $" + cost + (5 * snackAmount)); 
            break;

            default: 
                System.out.println("Not a valid option."); 
            break;

            }
        }
        while(snackChoice != 9);

其余部分:https://pastebin.com/Y6Xd24D0

它有效。实际结果:没有。

错误:snackChoice 无法解析为变量

Answer 1

do...while 循环是一个代码块，这意味着在其中定义的变量在代码块之外是看不到的。 while 部分位于 block 之外，因此它看不到 snackChoice。

只需在do...while之前定义int SnackChoice，不在其中:

int snackChoice;
do {
    System.out.println("Would you like to add any snacks? ");
    System.out.println("1: ($5) Large Popcorn");
    System.out.println("2: ($0) Nothing Else");
    snackChoice = input.nextInt();

    System.out.println("How many of option " + snackChoice + " would you like? ");
    System.out.println("1: One");
    System.out.println("2: Two");
    System.out.println("3: Three");
    System.out.println("4: Four");
    System.out.println("5: Five");
    int snackAmount = input.nextInt();

    switch (snackChoice) { 
    case 1: 
        cost = cost + 5 * snackAmount;
        System.out.println("Your total before tax will be: $" + cost + (5 * snackAmount)); 
    break;

    default: 
        System.out.println("Not a valid option."); 
    break;

    }
}
while(snackChoice != 9);