Question

I am learning Java and have a rather simple program that returns a series of numbers in accordance with the Collatz Conjecture. I can have it output into the console or have many JOptionPane.showMessageDialog() windows pop up, one with each number in it.

How would I combine the JOptionPane.showMessageDialog()‘s to show all the outputs in one JOptionPane.showMessageDialog()?

Code:

package collatz;

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

public class Collatz {

/**
 * Demonstrates the Collatz Cojecture
 * with a randomly generated number
 */

public static void main(String[] args) {
    Random randomGenerator = new Random();
    int n = randomGenerator.nextInt(1000);

    JOptionPane.showMessageDialog(null, "The randomly generated number was: " + n);


    while(n > 1){
        if(n % 2 == 0){
            n = n / 2;
            JOptionPane.showMessageDialog(null, n);
        }
        else{
            n = 3 * n + 1;
            JOptionPane.showMessageDialog(null, n);
        }
    }

    JOptionPane.showMessageDialog(null, n);
    JOptionPane.showMessageDialog(null, "Done.");

}

}

Thanks!

—
ZuluDeltaNiner

Answer 1

Keep track of the full string to be displayed, then display it at the end:

public static void main(String[] args) {
    Random randomGenerator = new Random();
    int n = randomGenerator.nextInt(1000);

    StringBuilder output = new StringBUilder("The randomly generated number was: " + n + "\n");

    while(n > 1){
        if(n % 2 == 0){
            n = n / 2;
        }
        else{
            n = 3 * n + 1;
        }
        output.append(n + "\n");
    }

    output.append("Done.");
    JOptionPane.showMessageDialog(null, output);

}