private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
 
        // import javax.swing.table.*;
 
        String [] [] data = { { "abc", "def" }, { "klm", "xyz"} };
 
        String [] titles = { "A", "B" };
 
        DefaultTableModel model = new DefaultTableModel (data, titles);
 
        jTable1.setModel (model);
 
        double [] [] cisla = {
                                {10, 20, 30},
                                {100, 200, 300},
                             };       
        display (cisla);
    }                                        
 
    public void display (double [] [] a)
    {
        int lines = a.length;
        int columns = 0;
        for (int i = 0; i < lines; i++)
            if (a[i].length > columns)
                columns = a[i].length;
 
        String [] [] data = new String [lines][columns];
 
        for (int i = 0; i < lines; i++)
            for (int j = 0; j < a[i].length; j++)
                data [i][j] = "" + a[i][j];
 
        String [] titles = new String [columns];
 
        DefaultTableModel model = new DefaultTableModel (data, titles);
 
        jTable1.setModel (model);
    }