在java中输入错误后询问用户另一个提示

Question

所以我要求用户一个月和一年.月份必须是十二个月中的一个,而一年必须是一个数字而不是字母.我试图弄清楚让程序说"输入错误,再试一次"的最佳方法,并再次提示他们输入.这是我正在为月份部分工作的代码部分.

public class MonthLength {
  public static void main(String[] args) {

     int month = 0;
    // Prompt the user to enter a month
    SimpleIO.prompt("Enter a month name: ");
    String userInput = SimpleIO.readLine();

      if (userInput.trim().toLowerCase().equals("january")) {
        month = 1;
      } else if (userInput.trim().toLowerCase().equals("february")) {
        month = 2;
      } else if (userInput.trim().toLowerCase().equals("march")) {
        month = 3;
      } else if (userInput.trim().toLowerCase().equals("april")) {
        month = 4;
      } else if (userInput.trim().toLowerCase().equals("may")) {
        month = 5;
      } else if (userInput.trim().toLowerCase().equals("june")) {
        month = 6;
      } else if (userInput.trim().toLowerCase().equals("july")) {
        month = 7;
      } else if (userInput.trim().toLowerCase().equals("august")) {
        month = 8;
      } else if (userInput.trim().toLowerCase().equals("september")) {
        month = 9;
      } else if (userInput.trim().toLowerCase().equals("october")) {
        month = 10;
      } else if (userInput.trim().toLowerCase().equals("november")) {
        month = 11;
      } else if (userInput.trim().toLowerCase().equals("december")) {
        month = 12;
      }


    // Terminate program if month is not a proper month name
    if (month < 1 || month > 12) {
      System.out.println("Illegal month name; try again");
      return;
    }

这就是我在年度部分工作的内容:

    // Prompt the user to enter a year
    SimpleIO.prompt("Enter a year: ");
    userInput = SimpleIO.readLine();
    int year = Integer.parseInt(userInput);

    //Here, trying to use hasNextInt to make sure input is an integer
    //If it's not, need to give an error message and prompt input again
    // public boolean hasNextInt()

    //Prompt input again if year is negative
    if (year < 0) {
       System.out.println("Year cannot be negative; try again");
       return;
    }

    // Determine the number of days in the month
    int numberOfDays;
    switch (month) {
      case 2:  // February
               numberOfDays = 28;
               if (year % 4 == 0) {
                 numberOfDays = 29;
                 if (year % 100 == 0 && year % 400 != 0)
                   numberOfDays = 28;
               }
               break;

      case 4:  // April
      case 6:  // June
      case 9:  // September
      case 11: // November
               numberOfDays = 30;
               break;

      default: numberOfDays = 31;
               break;
    }

    // Display the number of days in the month
    System.out.println("There are " + numberOfDays +
                       " days in this month");
  }
}

看到代码之后我肯定会更清楚我在问什么.如果他们输入一个不是一个月的单词,请提示他们并再次请求输入.如果他们进入一个非整数的年份,同样的事情.提前致谢!

Answer 1

在循环中运行它将:

String userInput;
int month;
do{
    SimpleIO.prompt("Enter a month name: ");
    userInput = SimpleIO.readLine();
    try{
        month = Integer.parseInt(userInput);
    } catch(NumberFormatException e){
        continue;
    }
}while(month <= 0 || month > 12);