How to set rows and columns of a JTable Dynamic

Question

my question is how to set dynamic, the number of rows and columns in a JTable? I mean if the user wants to create a table of 2 rows and 2 columns, he just type down the number. How can I do that, I've tried with the DefaultModel with no success.

I will appreciate any help.

Thanks

Answer 1

DefaultTableModel has two means by which you can define the number of rows/columns at runtime.

You could...

Simply create a new DefaultTableModel, passing it the rows and columns you want...

DefaultTableModel model = new DefaultTableModel(rows, cols);

and then apply this to the JTable. This will, obviously, replace the existing table model, meaning you will lose all of it's data.

You could...

Create an master DefaultTableModel and apply it to the JTable and simply use

model.setRowCount(rows);
model.setColumnCount(cols);

to dynamically update the number of rows and columns as required. This will allow you to preserve the data within the table model (expect when you remove rows or columns, then it's lost)

Runnable example

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSpinner;
import javax.swing.JTable;
import javax.swing.SpinnerNumberModel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.table.DefaultTableModel;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTable table;
        private DefaultTableModel model;
        private JSpinner fldRows;
        private JSpinner fldColumns;

        public TestPane() {

            setLayout(new BorderLayout());

            fldRows = new JSpinner(new SpinnerNumberModel(1, 1, 999999, 1));
            fldColumns = new JSpinner(new SpinnerNumberModel(1, 1, 999999, 1));

            JPanel options = new JPanel(new GridBagLayout());
            options.add(new JLabel("Rows: "));
            options.add(fldRows);
            options.add(new JLabel("Columns: "));
            options.add(fldColumns);

            JButton update = new JButton("Update");
            options.add(update);

            update.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    int rows = (int) fldRows.getValue();
                    int cols = (int) fldColumns.getValue();

                    // Dynamic master model...
//                  model.setRowCount(rows);
//                  model.setColumnCount(cols);

                    // Replace model
                    table.setModel(new DefaultTableModel(rows, cols));
                }
            });

            model = new DefaultTableModel();
            table = new JTable();
            add(new JScrollPane(table));
            add(options, BorderLayout.NORTH);

        }

    }

}

For more details, see...

• How to Use Tables
• How to Use Spinners