Invalid sorting on Date in JTable

Question

Please have a look at the below code

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
import javax.swing.table.*;

public class TableBasic extends JFrame
{
    public TableBasic()
    {

        String[] columnNames = {"Date", "String", "Long", "Boolean"};
        Object[][] data =
        {
            {getJavaDate("13-11-2020"), "A", new Long(1), Boolean.TRUE },
            {getJavaDate("13-11-2018"), "B", new Long(2), Boolean.FALSE},
            {getJavaDate("12-11-2015"), "C", new Long(9), Boolean.TRUE },
            {getJavaDate("12-11-2015"), "D", new Long(4), Boolean.FALSE}
        };

        final JTable table = new JTable(data, columnNames);
        table.setPreferredScrollableViewportSize(table.getPreferredSize());
        table.setAutoCreateRowSorter(true);
        table.getColumnModel().getColumn(0).setCellRenderer(tableCellRenderer);

        // DefaultRowSorter has the sort() method
        DefaultRowSorter sorter = ((DefaultRowSorter)table.getRowSorter()); 
        ArrayList list = new ArrayList();
        list.add( new RowSorter.SortKey(0, SortOrder.DESCENDING) );
        sorter.setSortKeys(list);
        sorter.sort();

        JScrollPane scrollPane = new JScrollPane( table );
        getContentPane().add( scrollPane );
    }

    private TableCellRenderer tableCellRenderer = new DefaultTableCellRenderer() 
    {

        SimpleDateFormat f = new SimpleDateFormat("dd-MM-yyyy");

        public Component getTableCellRendererComponent(JTable table,Object value, boolean isSelected, boolean hasFocus,int row, int column) 
        {
            if( value instanceof Date) 
            {
                value = f.format(value);
            }
            return super.getTableCellRendererComponent(table, value, isSelected,hasFocus, row, column);
        }
    };

    private Date getJavaDate(String s)
    {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
            Date d = sdf.parse(s);
             return d;

        } catch (ParseException ex) {
            Logger.getLogger(TableBasic.class.getName()).log(Level.SEVERE, null, ex);
            return null;
        }
    }



    public static void main(String[] args)
    {
        TableBasic frame = new TableBasic();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }
}

Now, just try to Sort it using the Date field. It is sorting it in an invalid way! Below is the result!

Why this is happening like this? I have even used cell render!

Answer 1

The table doesn't know that the column always contains Date instances and that it must thus sort chronologically, unless you give it that information, by overriding the getColumnClass() method of the table model:

final Class<?>[] columnClasses = new Class<?>[] {Date.class, String.class, Long.class, Boolean.class};

DefaultTableModel model = new DefaultTableModel(...) {
    @Override
    public Class<?> getColumnClass(int column) {
        return columnClasses[column];
    }
});
JTable table = new JTable(model);

Additional bonus: the numeric and boolean columns will then automatically rendered and sorted correctly.

Answer 2

@ Sniper not an answert, but I can't resist, because your code is very complicated, wrong designed, miss there lighweight required for ...

The key element missing is the override of TableModel.getColumnClass(), this is essential for table sorting to function

import java.awt.*;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.table.*;

public class TableBasic {

    private JFrame frame = new JFrame();
    private  String[] columnNames = {"Date", "String", "Long", "Boolean"};
    private Object[][] data = {
        {getJavaDate("13-11-2020"), "A", new Double(1), Boolean.TRUE},
        {getJavaDate("13-11-2018"), "B", new Double(2), Boolean.FALSE},
        {getJavaDate("12-11-2015"), "C", new Double(9), Boolean.TRUE},
        {getJavaDate("12-11-2015"), "D", new Double(4), Boolean.FALSE}
    };
    private DefaultTableModel model = new DefaultTableModel(data, columnNames) {
        @Override
        public Class<?> getColumnClass(int column) {
            return getValueAt(0, column).getClass();
        }
    };
    private JTable table = new JTable(model);
    private JScrollPane scrollPane = new JScrollPane(table);
    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("dd/MM/yyyy");

    public TableBasic() {
        table.setPreferredScrollableViewportSize(table.getPreferredSize());
        table.setAutoCreateRowSorter(true);
        setRenderers();
        // DefaultRowSorter has the sort() method
        table.getRowSorter().toggleSortOrder(0);
        frame.add(scrollPane);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private void setRenderers() {
        //TableColumnModel m = table.getColumnModel();
        //"Integer", "String", "Interger", "Double", "Boolean", "Double", "String", "Boolean", "Date"
        table.setDefaultRenderer(Date.class, new DateRenderer());
    }

    private Date getJavaDate(String s) {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
            Date d = sdf.parse(s);
            return d;

        } catch (ParseException ex) {
            Logger.getLogger(TableBasic.class.getName()).log(Level.SEVERE, null, ex);
            return null;
        }
    }

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                TableBasic frame = new TableBasic();
            }
        });
    }

    private class DateRenderer extends DefaultTableCellRenderer {

        private static final long serialVersionUID = 1L;

        @Override
        public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
            if (!(value instanceof Date)) {
                return this;
            }
            setText(DATE_FORMAT.format((Date) value));
            return this;
        }
    }
}