JTable set column data type

[Martin Zemanek]

Hi folks.
Is it possible to set a column in JTable to a certain data type? I mean to set a column to integer data type for example and when is user trying to input non-integer value it will do nothing.
Or do I have to solve this in other way like adding a listener and conditions to all cells in the column?
Martin

[Rob Spoor]

Check out TableModel.getColumnClass(int column). If this method returns Boolean.class, Integer.class (or any of the other Number subclasses), Date.class and a few others, a JTable will have automatic support for rendering / editing. For Integer.class that means that the editor will not accept the value and show a red border around the editor if the value cannot be converted into an int.

The easiest way is to subclass DefaultTableModel and override getColumnClass.

[Martin Zemanek]

Thanks for reply Rob.
But this TableModel.getColumnClass(int column) did not solve my problem. I have created a JTable using Object[cells][columnNames] and so all the cells are Object data type. I would like to set column class instead of get column class.
I do not quite understand this sentence:

The easiest way is to subclass DefaultTableModel and override getColumnClass.

I do not know how to subclass something. I was thinking about overriding it, but I do not know how and I am not sure it will help.
The other my idea is to create a JTable using Vector type, but i do not know if there will be more options to set column data type and also I am afraid it will cost me much more time to convert my table to Vector type.
Martin

[Rob Spoor]

How to Use Tables

[Darryl Burke]

Martin Zemanek wrote:I do not know how to subclass something.

Every Java class you've ever written subclassed something. Either you extended another class explicitly, or the class you wrote extended (subclassed) java.lang.Object implicitly.

[Martin Zemanek]

I have read How to Use Tables but it did not help me much. So I attach a shortened example of code and I would be happy if someone showed me the exact solution.

   public class ColumnDataType {

    public static void main(String[] args) {
        int rowCount = 5;
        String[] colNames = {"Name", "Age", "Date of birth"};
        Object[][] cells = new Object[rowCount][colNames.length];
        
        //creating a frame
        JFrame frame = new JFrame("Table");
        frame.setPreferredSize(new Dimension(300,200));
        frame.setVisible(true);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //creating a table
        DefaultTableModel mod = new DefaultTableModel(cells, colNames);
        JTable table = new JTable(mod);
        table.setVisible(true);

        //creating a scroll pane
        JScrollPane jsp = new JScrollPane(table);
        jsp.setVisible(true);

        table.repaint();    //frame is emtpy without this method
        frame.add(jsp);

    }

} 

At the beginning is the table empty, user can input values into cells, but it will not let him to enter a non-integer value into "age" column for example. I was searching the web, but the solutions I found did not helped me (or I did not understand). So I would like to see the solution on this example, if it is possible.
Martin

[Campbell Ritchie]

Now a candidate to move to our GUIs forum.

[Rob Camick]

Where did you override the getColumnClass(...) method? If you don't know how to do this then search the forum or the web for examples that use that method.

[Martin Zemanek]

Thanks for replies guys. So I subclassed DefaultTableModel and overridden some methods (getColumnClass, isCellEditable). If anyone else is interested in this so here is the solution.

  public class ColumnDataType {

      public static void main(String[] args) {
        int rowCount = 5;
        String[] columnNames = {"Name", "Age", "Date of birth"};
        Object[][] data = new Object[rowCount][columnNames.length];
        
        //creating a frame
        JFrame frame = new JFrame("Table");
        frame.setPreferredSize(new Dimension(300,200));
        frame.setVisible(true);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //creating a table
        MyTableModel mod = new MyTableModel(data, columnNames);
        JTable table = new JTable(mod);
        table.setVisible(true);
        table.getColumnClass(1);
        table.isCellEditable(1, 0);

        //creating a scroll pane
        JScrollPane jsp = new JScrollPane(table);
        jsp.setVisible(true);
        
        frame.add(jsp);

        jsp.revalidate();
        jsp.repaint();
    }

}

class MyTableModel extends DefaultTableModel {

    public MyTableModel(Object rowData[][], Object columnNames[]) {
         super(rowData, columnNames);
      }
   
    @Override
      public Class getColumnClass(int col) {
        if (col == 1)       //second column accepts only Integer values
            return Integer.class;
        else return String.class;  //other columns accept String values
    }

    @Override
      public boolean isCellEditable(int row, int col) {
        if (col == 0)       //first column will be uneditable
            return false;
        else return true;
      }
    }  

[Simon Wielki]

You can easly make column types in JTable (I use JXTable but in this thing it is the same):

    TableModel data = new DefaultTableModel() {
        Class[] types = new Class [] {
            //COL. TYPES ARE HERE!!!
            java.lang.String.class, java.lang.Object.class, java.lang.Integer.class, java.lang.Object.class
        };
        
        @Override
        public Class getColumnClass(int columnIndex) {
            return types [columnIndex];
        }
    };
    
    ((DefaultTableModel)data).setColumnCount(4);
    ((DefaultTableModel)data).setColumnIdentifiers(new Object[] {"Col. A", "Col. B", "Col. C", "Col. D"});
    //((DefaultTableModel)data).setRowCount(1);
    ((DefaultTableModel)data).addRow(new Object[] {"Dane A", "Dane B", 1, "Dane D"});
    ((DefaultTableModel)data).addRow(new Object[] {"Dane 1", "Dane 2", 2, "Dane 4"});
    ((DefaultTableModel)data).addRow(new Object[] {"1", "2", 3, "4"});
    ((DefaultTableModel)data).addRow(new Object[] {"A1", "A2", 12, "14"});
    
    jXTable1.setModel(data);

[Rob Spoor]

Welcome to the Ranch!

That code is horrible with all these casts. If you need to treat the model as a DefaultTableModel, simply declare it as such:

DefaultTableModel data = new DefaultTableModel()
...