Java applets seem to double-prompt

Question

When running a java applet that I made (a basic little number-guessing game), whenever it asks a question, be it yes/no or otherwise, it asks the first few questions, and does the standard procedure for the results, then opens the next question and reopens the previous set of questions. This goes on for quite a while, and does not stop at all until you close out of the html file. I'd like to be able to see if my game actually works, and possibly play it, though it's simple. Can anyone help with this problem?

Whole code for completion, but the first few questions are the real source of the problem.

import java.applet.Applet;
import java.awt.Graphics;
import javax.swing.JOptionPane;
import java.util.Random;

public class HelloWorld extends Applet {

    public void paint(Graphics g) {

        g.drawString ("James mylastname", 50, 25);
        String ans1 = JOptionPane.showInputDialog("Please input a value");
        String ans2 = JOptionPane.showInputDialog("Please input another value");
        String ans3 = JOptionPane.showInputDialog("Please input a final value");
        double ans1double = Double.parseDouble(ans1);
        double ans2double = Double.parseDouble(ans2);
        double ans3double = Double.parseDouble(ans3);
        double total = ans1double+ans2double+ans3double;
        double average = total/3;
        String answer = Double.toString (average);
        g.drawString ("The average of these three numbers is " + answer, 50, 50);

        Random generator = new Random();
        int x = generator.nextInt(100);
        x++;
        int i;
        // attribute names should be firstWordLowerCase
        int Prime = 5;
        for (i=2; i < x ;i++ ) {
            int n = x%i;
            if (n==0) {
                Prime = 1;
            } else {
                Prime = 0;
            }
        }

        g.drawString ("A random number has been generated, from 0 to 100. " +
            "Follow the dialogue boxes to guess the number. You have three " +
            "chances, and three hints.", 50, 75);
        int even;
        even = JOptionPane.showConfirmDialog(this, "Do you think the number is even?");
        if (even == 0) {
            if (x%2 == 0) {
                g.drawString ("Yes, this number is even.", 50,75);
            }
            if (x%2 != 0) {
                g.drawString ("No, this number is not even.", 50,75);
            }
        }

        if (even == 1) {
            if (x%2 == 0) {
                g.drawString ("Incorrect. This number is even.", 50,75);
            }
            if (x%2 != 0) {
                g.drawString ("Correct. This number is not even.", 50,75);
            }
        }

        // very bad idea to name one attribute 'Prime' and another 'prime'
        int prime;
        prime = JOptionPane.showConfirmDialog(this, "Do you think the number is prime?");
        if (prime == 0) {
            if (Prime == 1) {
                g.drawString ("Sorry, the number is not prime.", 50, 100);
            }
            if (Prime == 0) {
                g.drawString ("Correct, the number is prime.", 50, 100);
            }
        }

        if (prime == 1) {
            if (Prime == 1) {
                g.drawString ("Correct, the number is prime.", 50, 100);
            }
            if (Prime == 0) {
                g.drawString ("Sorry, the number is not prime.", 50, 100);
            }
        }

        int moreless;
        moreless = JOptionPane.showConfirmDialog(this, "Do you think the number is 50 or lower?");
        if (moreless == 0) {
            if (x <= 50) {
                g.drawString ("Correct. The number is 50 or less.", 50, 125);
            }
            if (x > 50) {
                g.drawString ("Incorrect. The number is higher than 50.", 50, 125);
            }
        }

        if (moreless == 1) {
            if (x<= 50) {
                g.drawString ("Incorrect. The number is lower than 50.", 50, 125);
            }
            if (x > 50) {
                g.drawString ("Correct. The number is higher than 50.", 50, 125);
            }
        }

        String guess1 = JOptionPane.showInputDialog("Please guess what you think the number is.");
        double guess1double = Double.parseDouble(guess1);
        if (guess1double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 150);
            return;
        }
        if (guess1double != x) {
            g.drawString ("Incorrect! Please guess again, you have two more tries!", 50, 150);
        }

        String guess2 = JOptionPane.showInputDialog("Please guess again.");
        double guess2double = Double.parseDouble(guess2);
        if (guess2double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 175);
            return;
        }

        if (guess2double != x) {
            g.drawString ("Incorrect! Please guess again, you have one more try!", 50, 150);
        }

        String guess3 = JOptionPane.showInputDialog("Please guess again.");
        double guess3double = Double.parseDouble(guess3);
        if (guess3double == x) {
            g.drawString ("Correct! You guessed the number!", 50, 200);
            return;
        }

        if (guess3double != x) {
            g.drawString ("Incorrect! Sorry, that was your last guess!", 50, 200);
        }
    }
}

Answer 1

You have UI creation code in your paint method which is called many times a second to render the applet view. This is the reason. You need to move that code to the init method, which is called once.

http://www.java2s.com/Code/Java/Swing-JFC/DemonstrationofAppletMethods.htm

http://www.cafeaulait.org/course/week5/28.html

Answer 2

The correct place to put those parts of the code that only need to be done once, is in the init() method.

DemoApplet.java

// <applet code='DemoApplet' width='400' height='400'></applet>
import java.applet.Applet;

public class DemoApplet extends Applet {

    @Override
    public void init() {
        System.out.println("init() once only at start-up");
    }

    @Override
    public void start() {
        System.out.println("start() potentially many times " +
            "(e.g. each time restored from minimized)");
    }

    @Override
    public void stop() {
        System.out.println("stop() potentially many times " +
            "(e.g. each time minimized)");
    }

    @Override
    public void destroy() {
        System.out.println("destroy() once only at shut down");
    }
}

Example I/O

prompt>appletviewer DemoApplet.java
init() once only at start-up
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
start() potentially many times (e.g. each time restored from minimized)
stop() potentially many times (e.g. each time minimized)
destroy() once only at shut down

Answer 3

The problem is that you have the code to prompt the user in your paint() method. That method is called by the AWT as many times as necessary to draw the content of your applet. Instead, move this code into a separate method that you know will only be called once. A good candidate is Applet.start().