Thread: How to output a pyramid of stars from a recursive method using JOptionPane

Hi,

here is my code so far. I was told we need to use two recursive methods. Any help will be very much appreciated. Thank you in advance.

 
 
package recursionexercise5;
 
import javax.swing.JOptionPane;
 
public class RecursionExercise5 {
 
    public static String saveStars(int n) {
 
        String stars, output;
 
        output = "";
 
        if (n == 0) {
 
            return "";
 
        } else {
 
            stars = "*";
 
 
            stars = stars + saveStars(n - 1);
 
           stars = stars + line(stars, n-1);
 
 
            System.out.println(stars);
 
            return stars;
        }
 
    }
 
    public static String line(String s, int num) {
 
        String st, output;
 
        if (num == 0) {
 
            return "";
 
        } else {
 
            return line(s += "\n", num - 1);
 
 
        }
 
    }
 
    public static void main(String[] args) {
 
        String sNum;
        int num, tStars;
 
        String stars;
 
        sNum = JOptionPane.showInputDialog("Enter the height");
 
        num = Integer.parseInt(sNum);
 
 
        stars = saveStars(num);
 
 
        JOptionPane.showMessageDialog(null, stars);
 
    }
 
}

Can you post the program's current output and add some comments saying what is wrong and show the desired output?


Note: The code has too many blank lines that make it harder to read and understand.

hi thank you for replying

the program's current output depends on the number that was passed. example if 4 was passed the output would be :

*
**
***
****

right now my code is only outputting " **** "

I need help in getting the full pyramid to output to the JOptionPane dialog box. I was told to use 2 recursive methods as a hint. my saveStars method is working
as it should but I know the problem is with my line method. The purpose of my line method is to save the string that it moves to a new line which makes sure the full pyramid is outputed to the JoptionPane dialog box

here is the code again :

import javax.swing.JOptionPane;
 
public class RecursionExercise5 {
 
    public static String saveStars(int n) {
 
        String stars, output;
 
        output = "";
 
        if (n == 0) {
 
            return "";
 
        } else {
 
            stars = "*";
 
            stars = stars + saveStars(n - 1);
 
           stars =  stars + line(stars, n-1);
 
            System.out.println(stars);
 
            return stars;
        }
 
    }
 
    public static String line(String s, int num) {
 
        if (num == 0) {
 
            return "";
 
        } else {
 
 
            return line(s += s + "\n", num - 1);
 
        }
 
    }
 
    public static void main(String[] args) {
 
        String sNum;
        int num, tStars;
 
        String stars;
 
        sNum = JOptionPane.showInputDialog("Enter the height");
 
        num = Integer.parseInt(sNum);
 
        stars = saveStars(num);
 
        JOptionPane.showMessageDialog(null, stars);
    }
 
}

purpose of my line method ...

That should be included as comments in the code so anyone reading the code will know what the method is supposed to do.

Please add comments to the code to describe what each method is supposed to do.
Reading the comments should enable anyone that reads them to understand what the code is trying to do.

The code still has too many blank lines.

Sorry for not adding comments. I have been struggling with the recursion unit so I tend to forget to add comments because I was too focused. The part I am having trouble is getting the previous line of stars to be saved instead of it only outputting the final line of the pyramid. As a hint my teacher said to use two recursive methods. The second method is the one I am having trouble with.

if 4 was passed into the saveStars method, the output should be :

*
**
***
****
but it is only outputing "****" which is the final line.


here is the code again:

 
package recursionexercise5;
 
import javax.swing.JOptionPane;
 
public class RecursionExercise5 {
 
//keeps adding stars to the the String "stars" until it reaches 0
// param n - the amount of stars
    public static String saveStars(int n) {
 
        String stars, 
 
        if (n == 0) {
            return "";
        } else {
            stars = "*";
            stars = stars + saveStars(n - 1);
            //this is supposed save the previous line of stars and then add a new line
           stars =  stars + line(stars, n-1);
            return stars;
        }
 
    }
 
//save the previous line of stars and then add a new line
    public static String line(String s, int num) {
        String st, output;
        if (num == 0) {
            return "";
        } else {
            return line(s += s + "\n", num - 1);
        }
 
    }
 
    public static void main(String[] args) {
 
        String sNum;
        int num, tStars;
 
        String stars;
        sNum = JOptionPane.showInputDialog("Enter the height");
        num = Integer.parseInt(sNum);
        stars = saveStars(num);
        //outputs the final pyramid of stars
        JOptionPane.showMessageDialog(null, stars);
 
    }
 
}

I'm not very good with recursion. Here is a link to a forum that has more academic helpers: http://www.coderanch.com/forums