如果其他陈述不起作用-为什么？

Question

在处理这段代码一段时间之后，我几乎遇到了一个意外的问题。当将选项“ B”和“ C”作为用户输入键入时，if和else语句在屏幕上不显示任何内容。我已经尝试了一些方法，但是似乎无法弄清楚。

import java.util.Scanner;
public class Internet_Service_Provider
{
    public static void main(String[] args)
    {
        double hours;
        char choice;

        Scanner input = new Scanner(System.in);

        System.out.println ("Enter the letter of your package: ");
        choice = input.nextLine().charAt(0);

        System.out.println ("Enter the number of hours used: ");
        hours = input.nextDouble();

        double chargesa, chargesb, chargesc;
        chargesa = 9.95;
        chargesb = 13.95;
        chargesc = 19.95;

        double chargesa2, chargesb2;
        chargesa2 = (hours - 10) * 2;
        chargesb2 = (hours - 20);

        double extrafeesA, extrafeesB;
        extrafeesA = chargesa + chargesa2;
        extrafeesB = chargesb + chargesb2;

        if (choice == 'A')
            if (hours <= 10) { 
                System.out.println ("Your total charges are: " + chargesa);
            }
        else if (choice == 'A')
            if (hours > 10){
                 System.out.println ("your total charges are: " + extrafeesA);
             }
        else if (choice == 'B')
            if (hours <= 20) {
                 System.out.println ("Your total charges are: " + chargesb);
            }
        else if (choice == 'B')
            if (hours > 20){
                 System.out.println ("Your total charges are: " + extrafeesB);
            }
        else if (choice == 'C'){
             System.out.println ("Your total charges are: " + chargesc);
        }
    }
}

当用户键入“ A”，然后键入小时数时，程序将完美运行，并为我提供所需的输出。如果输入“ B”或“ C”，然后输入小时数，则屏幕上没有输出。是什么原因造成的？

-EDIT-在检查响应之前弄乱了代码，发现如果删除else并创建此代码，则：

  if (choice == 'A')
        if (hours <= 10) { 
              System.out.println ("Your total charges are: " + chargesa);
        }

  if (choice == 'A')
        if (hours > 10){
              System.out.println ("your total charges are: " + extrafeesA);
        }

  if (choice == 'B')
        if (hours <= 20) {
              System.out.println ("Your total charges are: " + chargesb);
        }

  if (choice == 'B')
        if (hours > 20){
              System.out.println ("Your total charges are: " + extrafeesB);
        }

  if (choice == 'C'){
        System.out.println ("Your total charges are: " + chargesc);}

...程序正常运行。我猜想else语句是不必要的，并引起了问题。

Answer 1

if (choice == 'A'){
    if (hours <= 10) { 
      System.out.println ("Your total charges are: " + chargesa);}
    else if (choice == 'A')
      if (hours > 10){
      System.out.println ("your total charges are: " + extrafeesA);}
    else if (choice == 'B')
      if (hours <= 20) {
      System.out.println ("Your total charges are: " + chargesb);}
    else if (choice == 'B')
      if (hours > 20){
      System.out.println ("Your total charges are: " + extrafeesB);}
    else if (choice == 'C'){
      System.out.println ("Your total charges are: " + chargesc);}
    }
}

仅添加一些适当的表即可表明，除了“ A”之外，您实际上没有涵盖其他任何情况。列表使代码看起来更清晰，因此更容易发现错误。您需要正确使用括号，因为现在您仅检查choice =='A'。如果没有，则您的代码不会执行任何操作。