Java Exceptions Prevent Closing The Program (when clicking X button)

Question

I've built a little random number generator using JOptionPane. The exceptions that I've written prevent the user from quitting the program when clicking the X button. I've done lots of research and tried several things but nothing seems to work.

Here's my code:

import javax.swing.JOptionPane;
import java.util.Random;

public class Generate {
    private int number;
    private int min;
    private int max;
    private int repeat;
    Random no = new Random();
    int x = 1;

    void generateNumber() {
        do {
            try {
                String from = (String) JOptionPane.showInputDialog(null, "Welcome to Random Number Generator!\n\nPlease insert your number range.\n\nFrom:", "Random Number Generator", JOptionPane.QUESTION_MESSAGE, null, null, "Enter Number");
                min = Integer.parseInt(from);

                String to = (String) JOptionPane.showInputDialog(null, "To:", "Random Number Generator", JOptionPane.QUESTION_MESSAGE, null, null, "Enter Number");
                max = Integer.parseInt(to);
                System.out.println();

                String count = (String) JOptionPane.showInputDialog(null, "How many numbers would you like?", "Random Number Generator", JOptionPane.QUESTION_MESSAGE, null, null, "Enter Number");
                repeat = Integer.parseInt(count);
                System.out.println();

                for (int counter = 1; counter <= repeat; counter++) {
                    number = no.nextInt(max - min + 1) + min;
                    JOptionPane.showMessageDialog(null, "Random number #" + counter + ": " + number, "Random Number Generator", JOptionPane.PLAIN_MESSAGE);
                }
               x = 2;
            } catch (NumberFormatException e) {
                  JOptionPane.showMessageDialog(null, "INPUT ERROR: please insert a number", "Random Number Generator", JOptionPane.ERROR_MESSAGE);
            } catch (Exception e) {
                  JOptionPane.showMessageDialog(null, "INPUT ERROR: the second number needs to be higher than the first", "Random Number Generator", JOptionPane.ERROR_MESSAGE);
                }
            } while(x == 1);
        }
}

Main:

  class RandomNumber {
    public static void main(String[] args) {
        Generate obj = new Generate();
        obj.generateNumber();
    }
}

This is what happens when I try to close the program

Answer 1

You don't test the from value after showInputDialog() invocations.

For example here :

String from = (String) JOptionPane.showInputDialog(null,...

After this call, You chain directly with

min = Integer.parseInt(from);

whatever the value of from.
If from is null you finish in this catch as null is not a number :

  catch (NumberFormatException e) {
        JOptionPane.showMessageDialog(null, "INPUT ERROR: please insert a number", "Random Number Generator",
        JOptionPane.ERROR_MESSAGE);
    }

And x has still 1 as value. So the loop condition is still true.

To solve your problem, you just to test the value returned by showMessageDialog() and if the value is null, let the user exits from the method.

Add this code at each time you retrieve a user input and that you want to enable the user to exit :

if (from == null) {
    return;
}