Проблема с IDE NetBeans при добавлении макета сетки

Я создал дизайн своего приложения с помощью программы net beans. Я хотел бы добавить сетку 30 * 30, похожую на судоку. На самом деле я пытаюсь нарисовать 30 * 30 квадратов для карты. Однако я не могу добавить это представление в свой код. Я искал много мест, но не могу найти ответ. Я открыт для ваших идей. Может ли кто-нибудь помочь мне в этой теме, пожалуйста? Спасибо !

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/


import java.awt.Color;
import java.awt.Container;
import java.awt.Font;
import java.awt.GridLayout;

import javax.swing.JTextField;


public class NewJFrame extends javax.swing.JFrame {

/**
 * Creates new form NewJFrame
 */
public NewJFrame() {
    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    getDirectionButton = new javax.swing.JButton();
    questionTitle = new java.awt.Label();
    questionText = new javax.swing.JTextField();
    jScrollPane1 = new javax.swing.JScrollPane();
    directionDescriptionArea = new javax.swing.JTextArea();
    walkingManButton = new javax.swing.JButton();
    java.awt.Panel mapPanel = new java.awt.Panel();

    jButton1 = new javax.swing.JButton();


    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("DSL For Streets\n");
    setPreferredSize(new java.awt.Dimension(1365, 730));

    getDirectionButton.setText("Get Direction");

    questionTitle.setFont(new java.awt.Font("Dialog", 3, 12)); // NOI18N
    questionTitle.setText("Please enter your question");

    directionDescriptionArea.setColumns(20);
    directionDescriptionArea.setRows(5);
    jScrollPane1.setViewportView(directionDescriptionArea);

    walkingManButton.setFont(new java.awt.Font("Tahoma", 3, 11)); // NOI18N
    walkingManButton.setIcon(new javax.swing.ImageIcon(getClass().getResource("walk.png"))); // NOI18N
    walkingManButton.setText("Get Suggested Route");
    walkingManButton.setFocusable(false);

    jButton1.setIcon(new javax.swing.ImageIcon(getClass().getResource("map.png"))); // NOI18N


    cells = new int[ROWS][COLS];
    tfCells = new JTextField[ROWS][COLS]; // allocate JTextField array

   // Container cp = getContentPane();
    //cp.setLayout(new GridLayout(ROWS, COLS));
mapPanel.setLayout(new GridLayout(ROWS, COLS));
    // Create 9x9 JTextFields and place on the GridLayout
    for (int row = 0; row < ROWS; row++) {
       for (int col = 0; col < COLS; col++) {
          tfCells[row][col] = new JTextField(); // allocate element of array
         mapPanel. add(tfCells[row][col]);  // ContentPane adds JTextField
          int number = puzzle[row][col];

          tfCells[row][col].setText("");  // empty
          tfCells[row][col].setHorizontalAlignment(JTextField.CENTER);
          tfCells[row][col].setFont(new Font("Monospaced", Font.BOLD, 20));
       }
    }

    javax.swing.GroupLayout mapPanelLayout = new javax.swing.GroupLayout(mapPanel);
    mapPanel.setLayout(mapPanelLayout);
    mapPanelLayout.setHorizontalGroup(
        mapPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(mapPanelLayout.createSequentialGroup()
            .addGap(181, 181, 181)
            .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 172, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(239, Short.MAX_VALUE))
        .addGroup(mapPanelLayout.createSequentialGroup()

            .addGap(0, 0, Short.MAX_VALUE))
    );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(36, 36, 36)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addComponent(getDirectionButton, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(questionTitle, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.PREFERRED_SIZE, 177, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(questionText, javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jScrollPane1)
                .addComponent(walkingManButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 451, Short.MAX_VALUE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(mapPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(46, 46, 46))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(39, 39, 39)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(questionTitle, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(18, 18, 18)
                    .addComponent(questionText, javax.swing.GroupLayout.PREFERRED_SIZE, 36, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(18, 18, 18)
                    .addComponent(getDirectionButton, javax.swing.GroupLayout.PREFERRED_SIZE, 31, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(25, 25, 25)
                    .addComponent(walkingManButton, javax.swing.GroupLayout.PREFERRED_SIZE, 48, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 359, Short.MAX_VALUE))
                .addComponent(mapPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
    );

    pack();
}// </editor-fold>

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new NewJFrame().setVisible(true);
        }
    });
}
// Variables declaration - do not modify
private javax.swing.JTextArea directionDescriptionArea;
private javax.swing.JButton getDirectionButton;
private javax.swing.JButton jButton1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextField jTextField3;
private javax.swing.JTextField questionText;
private java.awt.Label questionTitle;
private javax.swing.JButton walkingManButton;
private javax.swing.JTextField a[]=new JTextField[30];
// End of variables declaration

public static final int ROWS = 9; // ROWS by COLS cells
public static final int COLS = 9;
public static final int CELL_SIZE = 10; // Cell width/height
public static final int CANVAS_WIDTH = CELL_SIZE * COLS;
public static final int CANVAS_HEIGHT = CELL_SIZE * ROWS;
private int[][] cells;
private JTextField[][] tfCells;
private int[][] puzzle =new int[9][9];

}