Thread: Seeking help with Grid/BorderLayout regarding Sudoku Puzzle program

Hello all. First off, I apologize if this is the wrong section for seeking this kind of help, I am a beginner programming student. I was assigned to create the gridlines for a Sudoku puzzle, which is basically a 3x3 grid, with a 3x3 grid within each of the nine box of the original grid. This puzzle does not have to function, I only have to create the grid (which is to be comprised of JTextFields) and some random, non-functioning buttons to the right of the puzzle. The original largest 3x3 grid must have a thick border (not just around the perimeter of the box, but the gridlines themselves), while the smaller 3x3 grids within must have thinner gridline borders.

My first inclination was to create a nested for loop to house a 3x3 grid within each square of another 3x3 grid. So I attempted to do that but came up short in the following code:

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
 
public class Sudoku1 extends JFrame {
	public Sudoku1(){
		// Create panel1 with GridLayout
		JPanel panel1 = new JPanel();
		JPanel panel3 = new JPanel();
		Border lineBorder = new LineBorder(Color.BLACK, 3);
		Border lineBorder2 = new LineBorder(Color.BLACK, 2);
 
		for (int i = 1; i <= 9; i++){
			panel1.setLayout(new GridLayout(3, 3));
			panel1.setBorder(lineBorder);
			panel1.add(new JTextField(1));
			for (int j = 1; j <= 9; j++){
				panel3.setLayout(new GridLayout(3, 3));
				panel1.setBorder(lineBorder2);
				panel1.add(new JTextField(1));
			}
		}
 
		JPanel panel2 = new JPanel(new BorderLayout());
		panel2.add(panel1, BorderLayout.CENTER);
 
		add(panel2, BorderLayout.CENTER);
		add(new JButton("Reset"), BorderLayout.EAST);
	}
 
	public static void main(String[] args){
		Sudoku1 frame = new Sudoku1();
		frame.setTitle("Sudoku Puzzle");
		frame.setSize(400, 400);
		frame.setLocationRelativeTo(null);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}
}

What it returns is this jumbled mess, essentially a 3x30 grid with untouched grid line borders:


If anyone could tell me where I went wrong in the original code and get me pointed in the right direction, I would greatly appreciate it. I figure it has to have something to do with the nested loop I implemented, but I cannot figure out what that might be.

Thank you for the response Jonathan. I am actually able to get the 3 by 3 grid just find. It is figuring out how to loop 9 more 3 by 3 grids within each grid square that has me stumped, unfortunately.

This works.

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
 
public class Sudoku1 extends JFrame {
	JPanel panel1 = new JPanel();
	Border exteriorBorder = new LineBorder(Color.BLACK, 3);
	Border dividerBorder = new LineBorder(Color.BLACK, 2);
 
	//constructor
	public Sudoku1(){
		for (int i = 1; i <= 9; i++){
			panel1.setLayout(new GridLayout(3, 3));
			panel1.setBorder(exteriorBorder);
			panel1.add(groupPanelMaker());
		}
 
		JPanel panel2 = new JPanel(new BorderLayout());
		panel2.add(panel1, BorderLayout.CENTER);
 
		add(panel1);
		add(new JButton("Reset"), BorderLayout.EAST);
	}
 
	//added a method to make inner groups of 9.
	public JPanel groupPanelMaker()
	{
		JPanel inner9 = new JPanel();
		for (int i = 1; i <= 9; i++){
			inner9.setLayout(new GridLayout(3, 3));
			inner9.setBorder(dividerBorder);
			inner9.add(new JTextField(1));
		}
		return inner9;
	}
 
	public static void main(String[] args){
		Sudoku1 frame = new Sudoku1();
		frame.setTitle("Sudoku Puzzle");
		frame.setSize(400, 400);
		frame.setLocationRelativeTo(null);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}
}

So I could see what you were doing, and played around with it for a while:
I tried creating the panels in reverse order, I tried dumbing it down to add panel 2 exactly twice.
but could only get your panel3 to show up once.
I came to the conclusion that it for some reason would not let you add the same object(in this case panel3) more then once.
So a wrote a method in your class to make an entire panel group, and return that panel group.
each panel group was added and it works and looks good.

I also renamed your border variables and since my method needed to use variables,
I took them out of your constuctor method and made them class varaibles.

You should post your understanding of how my code works step by step if you intend to cut and paste it for credit. (to not do so will only hurt your understanding in later classes)

Hear from you soon,
Jonathan

Thanks so much man, reading your explanation and looking at your code helps tremendously.
You essentially eliminated my nested loop and replaced it with a method that performed almost the same thing I was shooting for?
Do you know exactly why it wouldn't let me add the aforementioned panel3 object in the original code that I posted? Is it a logical error on my part of some sort?

I can't explain it either. However an interesting test let me try to break my method to get the same results as before the fix.

I have isolated the funny behavior, but still don't understand why it behaves this way.
None the less I was right about it not accepting the same object to add twice.
Below is identical code with 1 difference.

ADDs JPanel2 to JPanel1 twice.

import java.awt.*;
import javax.swing.*;
 
public class Sudoku2 extends JFrame {
	JPanel panel1 = new JPanel();
	JPanel panel2 = new JPanel();
	JPanel panel3 = new JPanel();
 
	public Sudoku2(){
		panel2.setLayout(new GridLayout(3, 3));
		panel2.add(new JTextField(1));
 
		panel3.setLayout(new GridLayout(3, 3));
		panel3.add(new JTextField(1));
 
 
		panel1.setLayout(new GridLayout(3, 3));
		panel1.add(panel2);
		panel1.add(panel2); // ONLY CHANGE
 
		add(panel1);
	}
 
	public static void main(String[] args){
		Sudoku2 frame = new Sudoku2();
		frame.setSize(400, 400);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}
}

Adds JPanel2 and JPanel3 to JPanel1

import java.awt.*;
import javax.swing.*;
 
public class Sudoku2 extends JFrame {
	JPanel panel1 = new JPanel();
	JPanel panel2 = new JPanel();
	JPanel panel3 = new JPanel();
 
	public Sudoku2(){
		panel2.setLayout(new GridLayout(3, 3));
		panel2.add(new JTextField(1));
 
		panel3.setLayout(new GridLayout(3, 3));
		panel3.add(new JTextField(1));
 
 
		panel1.setLayout(new GridLayout(3, 3));
		panel1.add(panel2);
		panel1.add(panel3); //ONLY CHANGE
 
		add(panel1);
	}
 
	public static void main(String[] args){
		Sudoku2 frame = new Sudoku2();
		frame.setSize(400, 400);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}
}

Compile them both and you will see the behavior, unfortunately I cant explain it. great question for the teacher!