title: asking user for another prompt after wrong input in java
body: <p>so i'm asking the user for a month and a year. month has to be one of the twelve months and year has to be a number and no letters. i'm trying to figure out the best way to make the program say "wrong input, try again" and prompt them for input again. here's the section of code i'm working with for the month section.</p>
  
  <pre><code>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 &lt; 1 || month &gt; 12) {
        System.out.println("Illegal month name; try again");
        return;
      }
  </code></pre>
  
  <p>and here's what i'm working with for the year section:</p>
  
  <pre><code>    // 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 &lt; 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 &amp;&amp; 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");
    }
  }
  </code></pre>
  
  <p>after seeing the code i'm sure it will be more clear what i'm asking. if they enter a word that isn't a month, prompt them and ask for input again. same thing if they enter a year that isn't integers. thanks in advance!</p>