URGENT HELP NEEDED FOR JTABLE PROBLEM!!!!!!!!!!!!!!!!!

Question

firstly i made a jtable to adds and deletes rows and passes the the data to the table model from some textfields. then i wanted to add a tablemoselistener method in order to change the value in the columns 1,2,3,4 and set the result of them in the column 5. when i added that portion of code the buttons that added and deleted rows had problems to function correctly..they dont work at all..can somebody have a look in my code and see wot is wrong..thanx in advance..
below follows the code..sorry for the mesh of the code..you can use and run the code and notice the problem when you press the add button..also if you want delete the TableChanged method to see that the add button works perfect.
* Created on 03-Aug-2005
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* @author Administrator
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import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;
import java.io.*;
public class NodesTable extends JFrame implements TableModelListener, ActionListener {
JTable jt;
DefaultTableColumnModel dtcm;
TableColumn column[] = new TableColumn[100];
DefaultTableModel dtm;
JLabel Name,m1,w1,m2,w2;
JTextField NameTF,m1TF,w1TF,m2TF,w2TF;
String c [] ={ "Name", "Assessment1", "Weight1" , "Assessment2","Weight2 ","TotalMark"};
float x=0,y=0,tMark=0,z = 0;
float j=0;
int i;
     JButton DelButton;
     JButton AddButton;
     JScrollPane scrollPane;
     JPanel mainPanel,buttonPanel;
     JFrame frame;
     Object[][] data =
          {"tami", new Float(1), new Float(1.11), new Float(1.11),new Float(1),new Float(1)},
          {"tami", new Float(1), new Float(2.22), new Float(2.22),new Float(1),new Float(1)},
          {"petros", new Float(1), new Float(3.33), new Float(3.33),new Float(1),new Float(1)},
          {"petros", new Float(1), new Float(4.44), new Float(4.44),new Float(1),new Float(1)}
public NodesTable() {
super("Student Marking Spreadsheet");
this.AddNodesintoTable();
setSize(400,250);
setVisible(true);
public void AddNodesintoTable(){
// Create a vector object and load them with the data
// to be placed on each row of the table
dtm = new DefaultTableModel(data,c);
dtm.addTableModelListener( this );
jt = new JTable(dtm){
     // Returning the Class of each column will allow different
          // renderers to be used based on Class
          public Class getColumnClass(int column)
               return getValueAt(0, column).getClass();
          // The Cost is not editable
          public boolean isCellEditable(int row, int column)
               int modelColumn = convertColumnIndexToModel( column );
               return (modelColumn == 5) ? false : true;
//****************************User Input**************************
//Add another node
//Creating and setting the properties
//of the panel's component (panels and textfields)
Name = new JLabel("Name");
Name.setForeground(Color.black);
m1 = new JLabel("Mark1");
m1.setForeground(Color.black);
w1 = new JLabel("Weigth1");
w1.setForeground(Color.black);
m2= new JLabel("Mark2");
m2.setForeground(Color.black);
w2 = new JLabel("Weight2");
w2.setForeground(Color.black);
NameTF = new JTextField(5);
NameTF.setText("Node");
m1TF = new JTextField(5);
w1TF = new JTextField(5);
m2TF=new JTextField(5);
w2TF=new JTextField(5);
//creating the buttons
JPanel buttonPanel = new JPanel();
AddButton=new JButton("Add Row");
DelButton=new JButton("Delete") ;
buttonPanel.add(AddButton);
buttonPanel.add(DelButton);
//adding the components to the panel
JPanel inputpanel = new JPanel();
inputpanel.add(Name);
inputpanel.add(NameTF);
inputpanel.add(m1);
inputpanel.add(m1TF);
inputpanel.add(w1);
inputpanel.add(w1TF);
inputpanel.add(m2);
inputpanel.add(m2TF);
inputpanel.add(w2TF);
inputpanel.add(w2);
inputpanel.add(AddButton);
inputpanel.add(DelButton);
//creating the panel and setting its properties
JPanel tablepanel = new JPanel();
tablepanel.add(new JScrollPane(jt, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED
, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS));
getContentPane().add(tablepanel, BorderLayout.CENTER);
getContentPane().add(inputpanel, BorderLayout.SOUTH);
//Method to add row for each new entry
public void addRow()
Vector r=new Vector();
r=createBlankElement();
dtm.addRow(r);
jt.addNotify();
public Vector createBlankElement()
Vector t = new Vector();
t.addElement((String) " ");
t.addElement((String) " ");
t.addElement((String) " ");
t.addElement((String) " ");
t.addElement((String) " ");
return t;
// Method to delete a row from the spreadsheet
void deleteRow(int index)
if(index!=-1) //At least one Row in Table
dtm.removeRow(index);
jt.addNotify();
// Method that adds and deletes rows
// from the table by pressing the
//corresponding buttons
public void actionPerformed(ActionEvent ae){
     Float z=new Float (m2TF.getText());
String Name= NameTF.getText();
Float x= new Float(m1TF.getText());
Float y= new Float(w1TF.getText());
Float j=new Float (w2TF.getText());
JFileChooser jfc2 = new JFileChooser();
String newdata[]= {Name,String.valueOf(x),String.valueOf(y),
String.valueOf(z),String.valueOf(j)};
Object source = ae.getSource();
if(ae.getSource() == (JButton)AddButton)
addRow();
if (ae.getSource() ==(JButton) DelButton)
deleteRow(jt.getSelectedRow());
//method to calculate the total mark in the TotalMark column
//that updates the values in every other column
//It takes the values from the column 1,2,3,4
//and changes the value in the column 5
public void tableChanged(TableModelEvent e) {
     System.out.println(e.getSource());
     if (e.getType() == TableModelEvent.UPDATE)
          int row = e.getFirstRow();
          int column = e.getColumn();
          if (column == 1 || column == 2 ||column == 3 ||column == 4)
               TableModel model = jt.getModel();
          float     q= ((Float)model.getValueAt(row,1)).floatValue();
          float     w= ((Float)model.getValueAt(row,2)).floatValue();
          float     t= ((Float)model.getValueAt(row,3)).floatValue();
          float     r= ((Float)model.getValueAt(row,4)).floatValue();
               Float tMark = new Float((q*w+t*r)/(w+r) );
               model.setValueAt(tMark, row, 5);
// Which cells are editable.
// It is only necessary to implement this method
// if the table is editable
public boolean isCellEditable(int row, int col)
{ return true; //All cells are editable
public static void main(String[] args) {
     NodesTable t=new NodesTable();
}

Answer 1

There are too many mistakes in your program. It looks like you are new to java.
Your add and delete row buttons are not working because you haven't registered your action listener with these buttons.
I have modifide your code and now it works fine. Just put some validation code for the textboxes becuase it throws exception when user presses add button without entering anything.
Here is the updated code: Do the diff and u will know my changes
* Created on 03-Aug-2005
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
* @author Administrator
* TODO To change the template for this generated type comment go to Window -
* Preferences - Java - Code Style - Code Templates
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;
import javax.swing.table.DefaultTableColumnModel;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableColumn;
import javax.swing.table.TableModel;
public class NodesTable extends JFrame implements TableModelListener,
          ActionListener {
     JTable jt;
     DefaultTableColumnModel dtcm;
     TableColumn column[] = new TableColumn[100];
     DefaultTableModel dtm;
     JLabel Name, m1, w1, m2, w2;
     JTextField NameTF, m1TF, w1TF, m2TF, w2TF;
     String c[] = { "Name", "Assessment1", "Weight1", "Assessment2", "Weight2 ",
               "TotalMark" };
     float x = 0, y = 0, tMark = 0, z = 0;
     float j = 0;
     int i;
     JButton DelButton;
     JButton AddButton;
     JScrollPane scrollPane;
     JPanel mainPanel, buttonPanel;
     JFrame frame;
     public NodesTable() {
          super("Student Marking Spreadsheet");
          this.AddNodesintoTable();
          setSize(400, 250);
          setVisible(true);
     public void AddNodesintoTable() {
          // Create a vector object and load them with the data
          // to be placed on each row of the table
          dtm = new DefaultTableModel(c,0);
          dtm.addTableModelListener(this);
          jt = new JTable(dtm) {
               // The Cost is not editable
               public boolean isCellEditable(int row, int column) {
                    int modelColumn = convertColumnIndexToModel(column);
                    return (modelColumn == 5) ? false : true;
          //****************************User Input**************************
          //Add another node
          //Creating and setting the properties
          //of the panel's component (panels and textfields)
          Name = new JLabel("Name");
          Name.setForeground(Color.black);
          m1 = new JLabel("Mark1");
          m1.setForeground(Color.black);
          w1 = new JLabel("Weigth1");
          w1.setForeground(Color.black);
          m2 = new JLabel("Mark2");
          m2.setForeground(Color.black);
          w2 = new JLabel("Weight2");
          w2.setForeground(Color.black);
          NameTF = new JTextField(5);
          NameTF.setText("Node");
          m1TF = new JTextField(5);
          w1TF = new JTextField(5);
          m2TF = new JTextField(5);
          w2TF = new JTextField(5);
          //creating the buttons
          JPanel buttonPanel = new JPanel();
          AddButton = new JButton("Add Row");
          AddButton.addActionListener(this);
          DelButton = new JButton("Delete");
          DelButton.addActionListener(this);
          buttonPanel.add(AddButton);
          buttonPanel.add(DelButton);
          //adding the components to the panel
          JPanel inputpanel = new JPanel();
          inputpanel.add(Name);
          inputpanel.add(NameTF);
          inputpanel.add(m1);
          inputpanel.add(m1TF);
          inputpanel.add(w1);
          inputpanel.add(w1TF);
          inputpanel.add(m2);
          inputpanel.add(m2TF);
          inputpanel.add(w2TF);
          inputpanel.add(w2);
          inputpanel.add(AddButton);
          inputpanel.add(DelButton);
          //creating the panel and setting its properties
          JPanel tablepanel = new JPanel();
          tablepanel.add(new JScrollPane(jt,
                    JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                    JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS));
          getContentPane().add(tablepanel, BorderLayout.CENTER);
          getContentPane().add(inputpanel, BorderLayout.SOUTH);
     //Method to add row for each new entry
     public void addRow() {
          Float z = new Float(m2TF.getText());
          String Name = NameTF.getText();
          Float x = new Float(m1TF.getText());
          Float y = new Float(w1TF.getText());
          Float j = new Float(w2TF.getText());
          String newdata[] = { Name, String.valueOf(x), String.valueOf(y),
                    String.valueOf(z), String.valueOf(j) };
          dtm.addRow(newdata);
     // Method to delete a row from the spreadsheet
     void deleteRow(int index) {
          if (index != -1) //At least one Row in Table
               dtm.removeRow(index);
               jt.addNotify();
     // Method that adds and deletes rows
     // from the table by pressing the
     //corresponding buttons
     public void actionPerformed(ActionEvent ae) {
          Object source = ae.getSource();
          if (ae.getSource() == (JButton) AddButton) {
               addRow();
          if (ae.getSource() == (JButton) DelButton) {
               deleteRow(jt.getSelectedRow());
     //method to calculate the total mark in the TotalMark column
     //that updates the values in every other column
     //It takes the values from the column 1,2,3,4
     //and changes the value in the column 5
     public void tableChanged(TableModelEvent e) {
          System.out.println(e.getSource());
          //if (e.getType() == TableModelEvent.UPDATE) {
               int row = e.getFirstRow();
               int column = e.getColumn();
               if (column == 1 || column == 2 || column == 3 || column == 4) {
                    TableModel model = jt.getModel();
                    float q = (new Float(model.getValueAt(row, 1).toString())).floatValue();
                    float w = (new Float(model.getValueAt(row, 2).toString())).floatValue();
                    float t = (new Float(model.getValueAt(row, 3).toString())).floatValue();
                    float r = (new Float(model.getValueAt(row, 4).toString())).floatValue();
                    Float tMark = new Float((q * w + t * r) / (w + r));
                    model.setValueAt(tMark, row, 5);
     // Which cells are editable.
     // It is only necessary to implement this method
     // if the table is editable
     public boolean isCellEditable(int row, int col) {
          return true; //All cells are editable
     public static void main(String[] args) {
          NodesTable t = new NodesTable();
}