private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
 
        // import javax.swing.table.*;
 
        String [] [] data =
        {
                {"abc", null,  null, null},
                {null,  "def", null, null},
                {null,  null,  null, null},
                {null,  null,  null, null}
        };
 
        String [] title = { "A", "B", "C", "D" };
 
        DefaultTableModel model = new DefaultTableModel (data, title);
 
        jTable1.setModel(model);
 
        double [] [] cisla  = { { 10, 20 },
                                 {100, 200} };
        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 [] title = new String [columns];
        for (int j = 0; j < columns; j++)
            title [j] = "" + (char) ('A' + j);
 
        DefaultTableModel model = new DefaultTableModel (data, title);
        jTable1.setModel(model);
    }