java - 当用户输入负值时如何退出程序 - Java

Question

扫描仪输入 = new Scanner(System.in);

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

Answer 1

这是因为您的测试仅在获得 3 个 double 值之后才执行。由于 input.nextDouble()，您应该在获取每个变量的值后立即移动与每个变量对应的测试。

您的代码应该是:

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:无需显式调用System.exit(0)，只需使用return即可。