JTable Columns not appearing

Question

I am trying to display a simple jtable in frame but It is not displaying the columns of the table, I followed the example from the oracle tutorials but there is something I am not doing right. The program is compiling and running. Here is the code:

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.math.BigDecimal;
import java.math.RoundingMode;

public class SimpleTableDemo extends JPanel 
{

    SimpleTableDemo()
    {
        String[] columnNames = {"#",
                "Repayment Dates",
                "Principle Amount",
                "Interest",
                "Comission fee",
                "Total installement amount", 
                "Principle balance"};

//      BigDecimal bd = new BigDecimal(d).setScale(2, RoundingMode.HALF_EVEN);
        //each line of the two dimentional array is a line in the table
        Object[][] data = {
                {new Integer(1), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(2), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(3), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(4), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(5), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(6), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(7), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(8), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(9), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(10), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(11), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(12), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(13), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(14), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(15), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(16), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(17), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
                {new Integer(18), new java.util.Date(), new BigDecimal(12509.23).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(1571.77).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(0.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(14081.00).setScale(2, RoundingMode.HALF_EVEN), new BigDecimal(147490.77).setScale(2, RoundingMode.HALF_EVEN)},
            };


        JTable table = new JTable(data, columnNames);

//      JScrollPane scrollPane = new JScrollPane(table);
//      scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
//      scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);    
        table.setFillsViewportHeight(true);
        this.add(table);
    }

    public static void main(String[] args)
    {
        JFrame application = new JFrame();
        SimpleTableDemo panel = new SimpleTableDemo();
        application.add(panel);
        application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//      application.setSize(730,650);
        application.pack();
        application.setLocationRelativeTo(panel);
//      application.setResizable(false);
        application.setVisible(true);
    }
}

Answer 1

Table columns are only automatically displayed if the JTable is inside a JScrollPane. Instead of this.add(table);, try this.add(new JScrollPane(table));

Actually, you seem to have some scrollpane-related code lying about already - just uncomment JScrollPane scrollPane = new JScrollPane(table); and change this.add(table); to this.add(scrollpane);

Answer 2

Having a JScrollPane always helps. You already have the following code:

JScrollPane scrollPane = new JScrollPane(table);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

All you need to do is add your JTable to this scrollpane.

However,I would suggest that any updates to the user interface to happen on the event dispatch thread. Basically, instead of having this:

 public static void main(String[] args)
    {
        JFrame application = new JFrame();
        SimpleTableDemo panel = new SimpleTableDemo();
        application.add(panel);
        application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//      application.setSize(730,650);
        application.pack();
        application.setLocationRelativeTo(panel);
//      application.setResizable(false);
        application.setVisible(true);
    }

Consider:

public static void main(String[] args)
{
    java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame application = new JFrame();
                SimpleTableDemo panel = new SimpleTableDemo();
                application.add(panel);
                application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            //      application.setSize(730,650);
                application.pack();
                application.setLocationRelativeTo(panel);
            //      application.setResizable(false);
                application.setVisible(true);
            }
        });
}

This article might help you understand the concept of "Threading with Swing"