Leap Year Calendar

Question

I am working on a project where the user enters a year. The string is then converted into an int and goes through a series of tests to see if it is a leap year or not. The problem I am having is when the user inputs letters when they are supposed to enter numbers. This gives the "java.lang.NumberFormatException" error. I used the try and catch code to make the user re input a year, but how do you make that into a loop. I want to make it so if the user keeps putting in letters, the computer keeps asking for numbers.
this is my code so far:
import javax.swing.JOptionPane; //import this at top
public class finding_the_leap_year {
public static void main(String[]args){
int year = 0;
{color:#ff0000}
try{
String inputValue = JOptionPane.showInputDialog("Input a year");
year = Integer.parseInt(inputValue);
catch(java.lang.NumberFormatException ex){
while(????????????????????){
System.out.println("Please enter a year");
String inputValue = JOptionPane.showInputDialog("Input a year");
year = Integer.parseInt(inputValue);
}          }{color}
if(year % 4 == 0)
System.out.println(year + " is a leap year.");
if(year % 100 == 0)
if(!(year%400==0)){
System.out.println(year + " is a leap year.");
else{
System.out.println(year + " is not a leap year.");
Edited by: chibioj on Sep 29, 2007 12:50 PM
Edited by: chibioj on Sep 29, 2007 12:51 PM

Answer 1

Put more in the while loop. I sometimes use a boolean value such as dataValid or inputValid and set it to false. I only set it to true if the input entered is ok. It is set to true in the try block but AFTER the data is obtained and parsed. The code will only reach that line if the input is valid.
        String inData = "";
        boolean dataValid = false;
        while (!dataValid) // while we don't have a correct answer yet
            try
                inData = JOptionPane.showInputDialog("Input a number");
                if (inData != null)  // if they didn't press the cancel button
                    year = Integer.parseInt(inData);                   
                dataValid = true; // won't get here if numberformatexception tripped
            catch (java.lang.NumberFormatException ex)
                JOptionPane.showMessageDialog(null, "You didn't enter a valid year.  Please try again.");
        if (inData != null) // if cancel button not pressed on input dialog
            if (......Also, you have some logic errors in the rest of your code that need fixing.
Good luck!