面向对象的用户输入编程

Question

如果输入正确的整数值之一，我的程序正常工作，输出正确 。我不确定如何解决它，就像我输入另一个值我只会得到“无效输入”（我放在我的代码中），但月份仍将是错误输入的整数。我需要知道如何在我的程序中解决这个问题。

import java.util.Scanner;

public class whichMonth {

    public static void main(String args[]){

        Scanner input = new Scanner(System.in);
        System.out.println("Please enter the month name or number: ");
        int monthNumber = input.nextInt();


        // set up variable access to the class
        AnyMonth inputMonthNumber = new AnyMonth();

        // set the month number from user input
        inputMonthNumber.setMonthnum(monthNumber);

        // get the month name from user input number
        String monthName = inputMonthNumber.getMonthName(monthNumber);

        // print out the month number and month name
        System.out.println("The month number is: " + inputMonthNumber.getMonthnum(monthNumber)
                + "\nThe month name is: " + inputMonthNumber.getMonthName(monthNumber));
    }
}

class AnyMonth {

   int Monthnum;
   String monthName;

   public AnyMonth() {

      Monthnum = 1;
   }
   public AnyMonth(int currentMonthNumber) {

      Monthnum = currentMonthNumber;

      switch(currentMonthNumber) {
         case 1:
            Monthnum = 1;
            monthName = "January";
            System.out.println("January");
            break;
         case 2:
            Monthnum = 2;
            monthName = "February";
            System.out.println("February");
            break;
         case 3:
            Monthnum = 3;
            monthName = "March";
            System.out.println("March");
            break;
         case 4:
            Monthnum = 4;
            monthName = "April";
            System.out.println("April");
            break;
         case 5:
            Monthnum = 5;
            monthName = "May";
            System.out.println("May");
            break;
         case 6:
            Monthnum = 6;
            monthName = "June";
            System.out.println("June");
            break;         
         case 7:
            Monthnum = 7;
            monthName = "July";
            System.out.println("July");
            break;         
         case 8:
            Monthnum = 8;
            monthName = "August";
            System.out.println("August");
            break;         
         case 9:
            Monthnum = 9;
            monthName = "September";
            System.out.println("September");
            break;         
         case 10:
            Monthnum = 10;
            monthName = "October";
            System.out.println("October");
            break;
         case 11:
            Monthnum = 11;
            monthName = "November";
            System.out.println("November");
            break;
         case 12:
            Monthnum = 12;
            monthName = "December";
            System.out.println("December");
            break;
         default:
            Monthnum = 1;
            monthName = "January";
      } 

   } 

   public AnyMonth(String userMonthName) {

      switch(userMonthName) {
         case "January":
            Monthnum = 1;
            monthName = "January";
            System.out.println("January");
            break;
         case "February":
            Monthnum = 2;
            monthName = "February";
            System.out.println("February");
            break;
         case "March":
            Monthnum = 3;
            monthName = "March";
            System.out.println("March");
            break;
         case "April":
            Monthnum = 4;
            monthName = "April";
            System.out.println("April");
            break;
         case "May":
            Monthnum = 5;
            monthName = "May";
            System.out.println("May");
            break;
         case "June":
            Monthnum = 6;
            monthName = "June";
            System.out.println("June");
            break;         
         case "July":
            Monthnum = 7;
            monthName = "July";
            System.out.println("July");
            break;         
         case "August":
            Monthnum = 8;
            monthName = "August";
            System.out.println("August");
            break;         
         case "September":
            Monthnum = 9;
            monthName = "September";
            System.out.println("September");
            break;         
         case "October":
            Monthnum = 10;
            monthName = "October";
            System.out.println("October");
            break;
         case "November":
            Monthnum = 11;
            monthName = "November";
            System.out.println("November");
            break;
         case "December":
            Monthnum = 12;
            monthName = "December";
            System.out.println("December");
            break;
         default:
            Monthnum = 1;
            monthName = "January";

      }    

   }

   public void setMonthnum (int userMonth) {

      Monthnum = userMonth;

      if (userMonth < 1 || userMonth > 12){
         System.out.println("Invalid input");
         this.Monthnum = userMonth;
      } 

   }

   public int getMonthnum(int currentMonthNumber) {

      Monthnum = currentMonthNumber;

      return currentMonthNumber;

   }

   public String getMonthName(int currentMonthName) {

      Monthnum = currentMonthName;
        // use swtich-case here instead, default case should return 1/Jan
      switch(currentMonthName) {
         case 1:
            monthName = "January";
            break;
         case 2:
            monthName = "February";;
            break;
         case 3:
            monthName = "March";
            break;
         case 4:
            monthName = "April";
            break;
         case 5:
            monthName = "May";
            break;
         case 6:
            monthName = "June";
            break;         
         case 7:
            monthName = "July";
            break;         
         case 8:
            monthName = "August";
            break;         
         case 9:
            monthName = "September";
            break;         
         case 10:
            monthName = "October";
            break;
         case 11:
            monthName = "November";
            break;
         case 12:
            monthName = "December";
            break;
         default:
            monthName = "January";

      }
      return monthName;
    }

    public String toString(String monthNameToString){

      monthName = monthNameToString;

      return monthNameToString;

    }

    public boolean equals(int month) {

        if (Monthnum == month) {
            return true;
        } 
        else {
            return false;
        }
    }

    public boolean greaterThan(int month) {

        if (Monthnum > month) {
            return true;
        } 
        else {
            return false;
        }
    }

    public boolean lessThan(int month) {

        if (Monthnum < month) {
            return true;
        } 
        else {
            return false;
        }

    }

}

Answer 1

首先，由于使用

，您的代码只会占用一个int

nextInt(); 

正在使用（如VVN所述）。

 int monthNumber = input.nextInt();

您的输出要求提供月份名称或号码，但您的程序只会接受一个号码。

接下来，您的程序默认为1月份和错误号码的原因是因为您处理错误案例的方式。

在setMonthnum（）方法中，您仍在设置Monthnum变量。

 if (userMonth < 1 || userMonth > 12){
     System.out.println("Invalid input");
     this.Monthnum = userMonth;
  } 

因此，您的程序将使用输入的任何不正确的int，并将继续执行。 1月开始显示为代码行

String monthName = inputMonthNumber.getMonthName(monthNumber);

正在通过switch语句查找错误的数字/输入。它没有找到匹配项，并使用默认情况1月。

default:
   monthName = "January";

如果你想解决这个问题，你应该添加某种形式的输入陷阱来提示用户输入另一个数字/输入，因为它们之前的数字/输入无效。如果您不希望提示输入其他内容，只需结束执行：

System.exit(0);

将停止执行而不会出现任何错误。但是，我强烈建议添加某种形式的输入陷阱来管理它。此外，如果您想在初始输入中实际接受月份名称，则可能需要使用

nextLine();

over nextInt。这将允许您将输入行作为字符串接收。从那里，您可以确定输入是月份的数字还是名称，并相应地采取行动（parseInt /使用月份名称）。