Pls help in Refreshing JTableModel

Question

I have defined 3 classes;
JDataBase
JTableModelClass
Expenditure
JDataBase class has the connection to the database and getData(String query) function.
JTableModel has a constructor with 2 parameters (String Query, Vector ColumnNames)
Expenditure is my UI class with JScrollPane and JTable which is being displayed.
*Problem</sOn the interface, i have a provision of the user specifying the columns he wants displayed. In case he wants to change the cols displayed, i have provided some checkboxes where after selecting/deselecting, a button click passes the query to the JTableModelClass which passes it to JDatabase class. The table is adjusted accordingly.
However, if i click on the colunm headers or the data rows, the initial table is displayed.
How cal i kill the first instance of the JTableModel before i run a fresh query? i.e. an equivalent of .dispose() method.
Why does it restore the first instance on table focus?

Answer 1

Ok Ok..i get it now. i was giving my questions a logical approach and not a programming one.
1) JDataBase Class
public class JDataBase {
public static Connection connection;
public static Statement statement;
ResultSet resultSet;
int regNo=0;
String[] columnNames = {};
Vector rows = new Vector();
ResultSetMetaData metaData;
public int no_rows;
/** Creates a new instance of JDataBase */
public JDataBase() {
System.out.println("In JDataBase Class");
public boolean connected(String url, String driverName,
String user, String passwd) {
boolean state=false;
try {
Class.forName(driverName).newInstance();
System.out.println("Opening db connection");
connection = DriverManager.getConnection(url, user, passwd);
statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
state=true;
catch (ClassNotFoundException ex) {
state=false;
System.err.println("Cannot find the database driver classes.");
System.err.println(ex);
catch(InstantiationException ins){
System.err.println("Cannot Instantiate the Driver.");
catch(IllegalAccessException iae){
System.err.println("IllegalAccessException.");
catch (SQLException ex) {
state=false;
System.err.println("Cannot connect to this database.");
System.err.println(ex);
return state;
* closes the db connection
public void close() {
try{
System.out.println("Closing db connection");
if(resultSet!=null)
resultSet.close();
if(statement!=null)
statement.close();
if(connection!=null)
connection.close();
}catch(SQLException ex){
System.out.println(ex.getMessage());
* @param query String
* @return Object
* returns a collectionof any values selected from the database
public Vector getData(String query) {
no_rows=0;
if (connection == null || statement == null) {
System.err.println("There is no database to execute the query.");
return new Vector();
try {
resultSet = statement.executeQuery(query);
metaData = resultSet.getMetaData();
int numberOfColumns = metaData.getColumnCount();
columnNames = new String[numberOfColumns];
// Get the column names and cache them.
// Then we can close the connection.
for(int column = 0; column < numberOfColumns; column++) {
columnNames[column] = metaData.getColumnLabel(column+1);
// Get all rows.
rows = new Vector();
while (resultSet.next()) {
no_rows++;
Vector newRow = new Vector();
for (int i = 1; i <= numberOfColumns; i++) {
newRow.addElement(resultSet.getObject(i));
rows.addElement(newRow);
// close(); Need to copy the metaData, bug in jdbc:odbc driver.
catch (SQLException ex) {
System.err.println(ex);
return rows;
public static void main(String[] args) {
JDataBase JDataBase1 = new JDataBase();
2) JTableModelClass
public class JTableModelClass extends AbstractTableModel {
Object [][] data;
JTable table;
Vector vectordata,rowdata;
String[] columnNames;
JDataBase db=new JDataBase();
/** Creates a new instance of JTableModelClass */
public JTableModelClass(String query, Vector colnames) {
columnNames=new String[colnames.size()];
String myquery=query;
String conn=db.connection.toString();
vectordata=db.getData(query);
for(int i=0;i<colnames.size();i++){
columnNames=(String)colnames.elementAt(i);
int rows=db.no_rows;
Object row;
data=new Object[rows][columnNames.length];
if(rows==0){
System.out.println("No Such Data Found");
} else{
System.out.println("Some Data Found");
for(int i=0;i<rows;i++){
rowdata=(Vector)vectordata.elementAt(i);
for(int j=0;j<columnNames.length;j++){
//data[i][j]=vectordata.elementAt(i);
data[i][j]=rowdata.elementAt(j);
System.out.println("making a table done");
public int getColumnCount() {
return columnNames.length;
public int getRowCount() {
return data.length;
public String[] getTableHeader(){
return columnNames;
public void addRow(Object[] row) {
for (int i=0; i<columnNames.length; i++) {
data[data.length+1][i] = row[i];
fireTableRowsUpdated(data.length+1,data.length+1);
public String getColumnName(int col) {
return columnNames[col];
public Object getValueAt(int row, int col) {
return data[row][col];
public Class getColumnClass(int c) {
return getValueAt(0, c).getClass();
3) Expenditure Class
public class Expenditures extends javax.swing.JFrame {
Vector fields;
JTable table;
String columns;
JScrollPane datascrollPane;
private void BtnOkActionPerformed(java.awt.event.ActionEvent evt) {                                     
// TODO add your handling code here:
displayData();
public void displayData(){
String fieldstring=" ";
Vector queryfields=checkFields();
if(fields.size()==0){
JOptionPane.showMessageDialog(this,"No field has been Selected","Select Field", JOptionPane.OK_OPTION);
int j=0;
for(j=0;j<queryfields.size();j++){
if(j==queryfields.size()-1) {
fieldstring +=(String)queryfields.elementAt(j).toString()+" ";
} else{
fieldstring +=(String)queryfields.elementAt(j).toString()+",";
String query="Select "+fieldstring +"from card_balances.balances_alloc";
tablemodel=new JTableModelClass(query, queryfields);
table = new JTable(tablemodel);
table.setPreferredScrollableViewportSize(new Dimension(500, 70));
table.setFillsViewportHeight(true);
table.setAutoCreateRowSorter(true);
datascrollPane = new JScrollPane(table);
datascrollPane.setBounds(10,300,(int)d.getWidth()-50,360);
this.jPanel1.add(datascrollPane);
public Vector checkFields(){
fields=new Vector();
String field1,field2;
int i=0;
if(this.medicalaidcode.isSelected()){
fields.addElement(medicalaidcode.getActionCommand());
i++;
if(this.Amount_alloc.isSelected()){
fields.addElement(Amount_alloc.getActionCommand());
i++;
if(this.Expenditure.isSelected()){
fields.addElement(Expenditure.getActionCommand());
i++;
if(this.balances_alloc.isSelected()){
fields.addElement(balances_alloc.getActionCommand());
i++;
if(this.Pool_nr.isSelected()){
fields.addElement(Pool_nr.getActionCommand());
i++;
if(this.Familynumber.isSelected()){
fields.addElement(Familynumber.getActionCommand());
i++;
if(this.Scheme_startdate.isSelected()){
fields.addElement(Scheme_startdate.getActionCommand());
i++;
if(this.Scheme_endDate.isSelected()){
fields.addElement(Scheme_endDate.getActionCommand());
i++;
if(this.PrincipleName.isSelected()){
fields.addElement(PrincipleName.getActionCommand());
i++;
if(this.mem_nr.isSelected()){
fields.addElement(mem_nr.getActionCommand());
i++;
if(this.PercentageEx.isSelected()){
fields.addElement(PercentageEx.getActionCommand());
i++;
if(this.EmailedDate.isSelected()){
fields.addElement(EmailedDate.getActionCommand());
i++;
if(this.CounterEmail.isSelected()){
fields.addElement(CounterEmail.getActionCommand());
i++;
return fields;
public String checkParameters(){
String conditions="";
String criteria, selected, startdate, enddate;
selected=this.RadioGroup.getSelection().getActionCommand();
startdate=this.DateFrom.getDate().toString();
enddate=this.DateTo.getDate().toString();
conditions="where ";
if(selected=="RadioPerFamily"){
} else if(selected=="RadioPerClient"){
} else{
return conditions;
* @param args the command line arguments
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Expenditures().setVisible(true);