Dynamically Updating JTable, please help

Question

I am trying to create an GUI for a java program I wrote to interface with motes running TinyOS. I am having some serious problems creating this because in the JTable tutorial everything is static so I can't figure out how I'm supposed to modify the table from my code. I'm basically reading packets coming in from the serial port and updating several data fields based on what is contained in the packet. I want certain cells in the JTable to reflect the changes that occur in the variables I have, sort of like a debugger would display, but in real time and at full run speed. I tried using the setValueAt function but the problem is the JTable is created in a static method and so I cannot call it from main. I tried moving the section of code that monitors the serial port and updates my data to the createAndShowGUI function, but unfortunately the table will not display unless this function returns, but the program will never return from this function if I move the code there and so I just get a completely grey JTable displayed. I have included the code below, sorry for the length of it but I need some help on this one, I was never taught java and am trying to learn this on my own for research purposes. As it stands now the only error generated by this code is from the following line:
newContentPane.DataTable.setValueAt("asdfsa",1,1);
I am not allowed access to newContentPane because it has been dynamically instantiated by createAndShowGUI and I cannot access it through main.
I'd appreciate any help on this, thank you.
package net.tinyos.tools;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JComponent;
import javax.swing.ListSelectionModel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Date;
import java.io.*;
import net.tinyos.packet.*;
import net.tinyos.util.*;
import net.tinyos.message.*;
public class BeaconListen extends JPanel {
private static int MAX_NODES = 10;
     JTable DataTable;
     public BeaconListen(){
     super(new GridLayout(1,0));     
     Object[] ColumnNames = {"Node","PPS","Average PPS","Time Elapsed"};
     Object[][] Data= {
     {"0","","",""},
     {"1","","",""},
     {"2","","",""},
     {"3","","",""},
     {"4","","",""},
     {"5","","",""},
     {"6","","",""},
     {"7","","",""},
     {"8","","",""},
     {"9","","",""},
     DataTable = new JTable(Data,ColumnNames);
     DataTable.setPreferredScrollableViewportSize(new Dimension(500, 70));
     JScrollPane scrollPane = new JScrollPane(DataTable);
add(scrollPane);
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
private static void createAndShowGUI(){
//Make sure we have nice window decorations.
JFrame.setDefaultLookAndFeelDecorated(true);
//Create and set up the window.
JFrame frame = new JFrame("MoteData");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
BeaconListen newContentPane = new BeaconListen();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
//Display the window.
frame.pack();
frame.setVisible(true);
     if (args.length > 0) {
     System.err.println("usage: java net.tinyos.tools.BeaconListen");
     System.exit(2);
     public static void main(String args[]) {
     //Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
               PacketSource reader = BuildSource.makePacketSource();
     if (reader == null) {
     System.err.println("Invalid packet source (check your MOTECOM environment variable)");
     System.exit(2);
          int i, total = 0;
     int reset =1;
     int packetcount[] = new int[MAX_NODES];
     int PL[] = new int[MAX_NODES];
     int counter[] = new int[MAX_NODES];
     double RSSI[]= new double[MAX_NODES];
     int signalStrength=0;
     double strengthUnsigned=0;
     int Transition=0;
     int PPS=0;
     int FirstRun=1;
     int packetHold=0;
     double avgPacketCount[] = new double[MAX_NODES];
     int secondsElapsed=0;
     int averageReset=1;
     int totalPacketsReceived[] = new int[MAX_NODES];
     System.out.println("Node Listening");
     try {
     reader.open(PrintStreamMessenger.err);
     for(;;){
          byte[] packet = reader.readPacket();
     if(reset==1)
     for(i=0; i<MAX_NODES; i++)
          packetcount=0;
          PL[i]=0;
          counter[i]=0;     
          if(averageReset==1)
          secondsElapsed=0;
          avgPacketCount[i]=0;
          totalPacketsReceived[i]=0;
     reset =0;
     if(FirstRun==0)
     packetcount[packetHold]++;
     totalPacketsReceived[packetHold]++;
     PPS++;
     FirstRun=0;
     averageReset=0;
     packetcount[packet[6]]++;
     totalPacketsReceived[packet[6]]++;
     PPS++;
     strengthUnsigned = ((int)packet[8])& 0xFF;
     RSSI[packet[6]]=RSSI[packet[6]]+strengthUnsigned;
if((packet[10]==1 && Transition==1) || (packet[10]==0 && Transition==0))
     secondsElapsed++;
     if(Transition==1)
     Transition=0;
     else
     Transition=1;
     PPS--;
     packetcount[packet[6]]--;
     totalPacketsReceived[packet[6]]--;
     packetHold=packet[6];
     reset=1;
     for(i=0; i<MAX_NODES; i++)
     newContentPane.DataTable.setValueAt("asdfsa",1,1);
          System.out.println("Packet Count for Node " + i + "is: " + packetcount[i]);
          PL[i]=8 - packetcount[i];
          System.out.println("Packet Loss for Node " + i + "is: " + PL[i]);
          avgPacketCount[i]=1.0*totalPacketsReceived[i]/secondsElapsed;
          System.out.println("Avg Packet Count for " + secondsElapsed + " seconds is: " +avgPacketCount[i]);
          if(RSSI[i]!=0)
          RSSI[i]=RSSI[i]/packetcount[i];
          RSSI[i]=3*(RSSI[i]/1024);
          RSSI[i]=(-51.3*RSSI[i])-49.2;
          System.out.println("RSSI(dBm) for node " + i + "is: " + RSSI[i]);
          System.out.println();
          packetcount[i]=0;
          RSSI[i]=0;
     System.out.println("Total Packets Recieved: " + PPS);
     PPS=0;
               System.out.println();
               System.out.println();
     javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
     catch (IOException e) {
     System.err.println("Error on " + reader.getName() + ": " + e);

Answer 1

The best way to update your data is using a TableModel :
When you instantiate a JTable with an array of objects, it creates a DefaultTableModel which actualy stores your data.
So, you should create your TableModel, and feed it with the data. Each time the data is updated, the TableModel must notify the JTable, so the new data can be shown :
here's a simple example
public class MyModel extends AbstractTableModel
Object[][] data;
//you must implement some abstract methods declared in AbstractTableModel
//the method you use to update the data (you can give it the name you want)
setData(Object[][] _data)
data=_data;
fireTableDataChanged();//method of AbstractTableModel that notifies the data has changed
public void main(String[] s)
MyModel tableModel = new MyModel();
JTable table = new JTable(tableModel);
JFrame frame = new JFrame();
frame.getContentPane().add((new JScrollPane()).getViewport().add(table);
frame.pack();
frame.setVisible(true);
tableModel.setData(new Object[][]{{"one", "two"}, {"three", "four"};
thread.sleep(5000);
tableModel.setData(new Object[][]{{"five", "six"}, {"seven", "eight};
You will see the table displaying one, two, three, four, during 5 seconds, and then it will display five, six...