JTable cell editor decimilization threshold

Question

I have a JTable that displays a column of doubles, and I'd like to limit the precision to 4 places. Using a custom cell renderer, this is straightforward; however, when a user selects a cell to edit the value, this also needs to truncate at four decimal places. I really don't want users to be able to enter something like 1.23423428384.

I've read many threads on cell editors, but can't find a minimum working example to do something this simple. Below I've posted a minimum working example of a table with stubbed example of editor. If anyone could fill in the stubbed methods to prevent users from entering > 4 decimals, that would be tremendously helpful.

package sandbox;

import java.awt.Component;
import javax.swing.AbstractCellEditor;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;
import javax.swing.table.TableCellEditor;

public class TableExample extends JFrame {

    public TableExample() {
        //headers for the table
        String[] columns = new String[]{
            "Id", "Name", "Hourly Rate", "Part Time"
        };

        //actual data for the table in a 2d array
        Object[][] data = new Object[][]{
            {1, "John", 40.0, false},
            {2, "Rambo", 70.0, false},
            {3, "Zorro", 60.0, true},};

        //create table with data
        JTable table = new JTable(data, columns);

        /**
         * SET EDITOR HERE
         */
        table.getColumnModel().getColumn(2).setCellEditor(new DecimalEditor());

        //add the table to the frame
        this.add(new JScrollPane(table));
        this.setTitle("Table Example");

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.pack();
        this.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TableExample();
            }
        });
    }

    public class DecimalEditor extends AbstractCellEditor implements TableCellEditor {

        @Override
        public Object getCellEditorValue() {
            throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        }

        @Override
        public Component getTableCellEditorComponent(JTable jtable, Object o, boolean bln, int i, int i1) {
            throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        }
    }

}

Answer 1

Try using a DefaultCellEditor .

The constructor will accept a JTextField as an editor.

However in your case you would want to create the editor using a JFormattedTextField . Then you can specify the MaskFormat that you want to limit the number of decimals.