用戶輸入負值時如何退出程序-Java

Question

掃描儀輸入=新的Scanner（System.in）;

    System.out.print("How much can you afford for meals per day? Enter it now ");
    double mealAmount = input.nextDouble();  

Answer 1

這是因為僅在獲得3個double值之后才執行測試。 input.nextDouble()獲得值之后，應立即移動與每個變量相對應的測試。

您的代碼應該是：

System.out.print("How much can you afford for meals per day? Enter it now ");
double mealAmount = input.nextDouble();  

if (mealAmount <0)
    System.exit(0);
else if (mealAmount < 15.00 && mealAmount >=0)
    System.out.println("No meal for you. Tough luck.");
else if (mealAmount >= 15.00 && mealAmount < 30.00)
    System.out.println("You can afford bronze meals.");
else if (mealAmount >= 30.00 && mealAmount < 60.00)
    System.out.println("You can afford silver meals.");
else if (mealAmount >= 60.00)
    System.out.println("You can afford gold meals.");
...

注意：無需顯式調用System.exit(0)即可，只需使用return 。