Question

I am New in java, I have a JTable that can read records from a txt file and show they perfectly.
I want to add a new book to my JFrame that when user select a row on table and clicked the “delete” button, that row should delete and that deleted row records must delete from txt file,too.
my code is this, but it has errors and not seen JTable! :

public class CopyOfAllUserTable extends AbstractTableModel {
Vector data;
Vector column;
public static void main(String[] args){
    new CopyOfAllUserTable();
}
public CopyOfAllUserTable() {

        String line;
        data = new Vector();
        column = new Vector();
        try {
        FileInputStream fis = new FileInputStream("D:\\AllUserRecords.txt");
        BufferedReader br = new BufferedReader(new InputStreamReader(fis));
      StringTokenizer st1 = new StringTokenizer(br.readLine(), " ");
              while (st1.hasMoreTokens())
               column.addElement(st1.nextToken());
                while ((line = br.readLine()) != null) {
                       StringTokenizer st2 = new StringTokenizer(line, " ");
                        while (st2.hasMoreTokens())
                                data.addElement(st2.nextToken());
                }
                br.close();
        } catch (Exception e) {
                e.printStackTrace();
        }

    final JFrame frame1=new JFrame();
     JTable table=new JTable(data,column);
    JButton button1=new JButton("Delete");


    button1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
           DefaultTableModel model=new DefaultTableModel(data, column);
           JTable table=new JTable(model);

        }
    });


    JPanel panel=new JPanel();
    panel.add(table);
    panel.add(button1);
    frame1.add(panel);
    frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame1.setBounds(200, 80, 600, 500);
    frame1.setVisible(true);
    frame1.setEnabled(true);


}

public int getRowCount() {
        return data.size() / getColumnCount();
}

public int getColumnCount() {
        return column.size();
}

public Object getValueAt(int rowIndex, int columnIndex) {
        return (String) data.elementAt((rowIndex * getColumnCount())
                        + columnIndex);
}

}

My problem is in delete row, and read records from file to jtable are perfectly successful.

Answer 1

Firstly you’re not adding your JTable to the content of the frame.

For containers like: frame.getContentPane() and JPanel you should add the child components by using their #add(...) method.

For example:

 final JPanel panel=new JPanel(new BorderLayout());
 button1.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
       DefaultTableModel model=new DefaultTableModel(data, column);
       JTable table=new JTable(model);
       panel.add(new JScrollPane(table));
       panel.revalidate();
    }
});

Note that JPanel default layout is FlowLayout. Second thing – if you want to have headers and scrolling in your JTable you need to wrap it with JScrollPane.
Next – you should revalidate the panel after adding/removing/etc.

The second issue is removing rows from JTable. I usually write a method to handle it:

protected void removeRows(final int[] rows) {
    int modelRows[] = new int[rows.length];
    for(int i = 0; i < rows.length; ++i) {
        modelRows[i] = table.convertRowIndexToModel(rows[i]);
    }
    Arrays.sort(modelRows);
    for(int i = modelRows.length - 1; i >= 0; --i) {
        int row = modelRows[i];
        model.removeRow(row);
    }
    model.fireTableDataChanged();
}

The convertRowIndexToModel method converts index returned by JTable#getSelectedRows() or JTable#getSelectedRow() (which are the visible indices) to the model indices. If you set RowSorter for your JTable or you leave it to standard implementation:

table.setAutoCreateRowSorter(true);