2

更新 当用户第一次做出诸如“1”之类的选择时，菜单会再次显示。下一次做出选择时，支付信息开始循环。循环完成并再次显示菜单后，它可以正常工作。此外，前两年是输出，而不是仅在选择开始循环时输出第一年，然后按预期一次输出一年。

//create scanner object for choosing a loan, then prompt for and accept input
    Scanner choose = new Scanner(System.in);
    String choice;
    System.out.println("\nType 1, 2, or 3 and press enter to see the monthly payment information for the respective loan. To end the program type \"end\".");
    choice = choose.next();

    //cycle loan 1 payment information
    //create scanner object to advance to the next year's payments

    //loop for cycling payment information
    //initialize loan principal to variable

    while (!"end".equals(choice)) {
        System.out.println("\nType 1, 2, or 3 and press enter to see the monthly payment information for the respective loan. To end the program type \"end\".");
        choice = null;
        choice = choose.next();
        if ("1".equals(choice)) {
           //calculation code
                    }
                if (j < 6) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = choose.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }

            }

            choice = null;
        }
        if ("2".equals(choice)) {
            //calculation code
                }
                if (j < 14) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = choose.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }

            }

            choice = null;
        }
        if ("3".equals(choice)) {
            //calculation code
                }
                if (j < 29) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = next.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }

            }

            choice = null;
        }
    }
    choose.close();
}

}

4

4 回答 4

5

我可以预先看到三个问题：

  1. 您不需要两个扫描仪来进行System.in流式传输。删除此语句Scanner next = new Scanner(System.in);并使用choose实例。

  2. 如果您将输入扫描仪关闭为next.close();，它也会关闭您的输入流System.in，您可能无法再次读取该流。确保仅在完全完成程序后才关闭流。

  3. 使用equals方法比较whileas中的条件while(!"end".equals(choice))。将文字"end"作为第一个参数将处理choice.

编辑：

您修改的高级代码：

    Scanner choose = new Scanner(System.in);
    String choice= null;
    int j = 0;
    while (!"end".equals(choice)) {
        System.out.println("\nType 1, 2, or 3 and press enter to see the monthly payment information for the respective loan. To end the program type \"end\".");
        choice = choose.nextLine();
        if ("1".equals(choice)) {
           //calculation code
               if (j < 6) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = choose.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }
            choice = null;
        }
        if ("2".equals(choice)) {
                if (j < 14) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = choose.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }
            choice = null;
        }
        if ("3".equals(choice)) {
                if (j < 29) {
                    System.out.println("Press enter to get the mortgage information for year " + (j + 2));
                    choice = choose.nextLine();
                } else {
                    System.out.println("Congratulations, your mortgage has been paid off.");
                }
            choice = null;
        }
    }
    choose.close();
于 2012-11-27T03:03:04.243 回答
1

导入 java.util.Scanner；

主类

{

public static void main(String [] args)

  {

    Scanner sc=new Scanner(System.in);

    System.out.println("Enter no.1:");

    int a=sc.nextInt();

    System.out.println("Enter no.2:");

    int b=sc.nextInt();

    boolean exit=false;

    do
    {
      System.out.println("1.addition");
      System.out.println("2.subtraction");
      System.out.println("3.multiplication");
      System.out.println("4.division");
      System.out.println("5.exit");
      System.out.println("choose one!");
      Scanner sd=new Scanner(System.in);
      System.out.println("enter your choice");
      int num=sd.nextInt();
      switch(num)
     {
       case 1:
       int add=a+b;
       System.out.println("addition="+add);
       System.out.println("\n");
       break;

       case 2:
       int sub=a-b;
       System.out.println("subtraction="+sub);
       System.out.println("\n");
       break;

       case 3:
       int mul=a*b;
       System.out.println("multilpication="+mul);
       System.out.println("\n");
       break;

       case 4:
       int div=a/b;
       System.out.println("division="+div);
       System.out.println("\n");
       break;

       case 5:
       exit=true;
       break;
      }
    }while(!exit);
}

}

于 2013-07-29T10:56:03.943 回答
1

一个错误是字符串相等与 == 不同。您应该使用 .equals()：

while (!choice.equals("end")) {

希望有帮助！

于 2012-11-27T03:00:42.047 回答
1

你设置choice为null，所以choice != "end"总是正确的。将next.close(); choice = null移到while 循环之外。另外，weolfe91 所说的。

于 2012-11-27T03:01:45.667 回答