I am trying to use a combo to generate query on the JTable.

Question

package tables; import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; import java.util.Vector; import javax.swing.*; import javax.swing.JFrame; import javax.swing.table.DefaultTableModel; public class Dynamictable extends JFrame {       public JComboBox combo;   JLabel labelz;   JPanel p1,scrollpanel;   String query;     public Dynamictable()     {                 p1 = new JPanel();         try{         JFrame frame = new JFrame("This is my table");         frame.addWindowListener(new WindowAdapter() {         public void windowClosing(WindowEvent e)         {             System.exit(0);         }         });         //Initializing the panel to contain the combox         p1 = new JPanel();         scrollpanel = new JPanel();         labelz = new JLabel("Select Matric Number or All -");               Combodata j = new Combodata();         Vector com =  j.setdata();         com.addElement("All");           String com1[] = new String[com.size()];         for(int i=0; i<com.size(); i++){       com1[i] = com.elementAt(i).toString();       combo = new JComboBox(com1);       System.out.println(com1);
p1.add(labelz);
p1.add(combo);
String data1,data2,data3,data4;
data1 = null;
data2 = null;
data3 = null;
data4 = null;
DefaultTableModel tablemodel = new DefaultTableModel();
//adding the connection into the datasource
String url = "jdbc:odbc:mydata";
Connection con = DriverManager.getConnection(url);
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Statement stat = con.createStatement();
query = "select * from Firstsemester;";
Myquery q = new Myquery();
q.sendQuery(combo);
ResultSet result = stat.executeQuery(query);
//while(result.next()){rows++;}
tablemodel.addColumn("Matric Number");
tablemodel.addColumn("Course");
tablemodel.addColumn("Point");
tablemodel.addColumn("Unit");
//Collecting the values into the vector
while(result.next())
Vector tabledata = new Vector();
data1 = result.getString("Matric_Number");
tabledata.addElement(data1);
data2 = result.getString("Courses");
tabledata.addElement(data2);
data3 = result.getString("Points");
tabledata.addElement(data3);
data4 = result.getString("Units");
tabledata.addElement(data4);
//getting rows
tablemodel.addRow(tabledata);
JTable table = new JTable(tablemodel);
JScrollPane scroll = new JScrollPane(table);
table.getParent().setSize(new Dimension(500,100));
scrollpanel.add(scroll);
scrollpanel.setSize(500,100);
JPanel panel = new JPanel();
panel.setLayout(new BorderLayout());
panel.add("North",p1);
panel.add("South",scrollpanel);
frame.getContentPane().add(panel);
frame.setVisible(true);
frame.setSize(500,500);
catch(Exception e)
System.out.println(e);
ComboListener combolisten = new ComboListener();
combo.addActionListener(combolisten);
public static void main(String args[])
new Dynamictable();
class ComboListener implements ActionListener
public void actionPerformed(ActionEvent evt)
String collectvalue= combo.getSelectedItem().toString();
String qry = "Select * from Firstsemester where Matric_Number = ";
String test = null;
if(collectvalue.equals("All"))
query = "Select * from Firstsemester;";
else
Myquery dt = new Myquery();
test = "'"+dt.sendQuery(combo)+"'";
qry+=test;
//query.contains(null);
query.contains(qry);
query.equals(qry);
System.out.print(query);
System.out.println(query);
class Combodata
public Vector setdata()
String data = null;
Vector elem = new Vector();
try{
//adding the connection into the datasource
String url = "jdbc:odbc:mydata";
Connection con = DriverManager.getConnection(url);
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Statement stat = con.createStatement();
ResultSet result = stat.executeQuery("select Matric_Number from Firstsemester;");
while(result.next())
data = result.getString("Matric_Number");
elem.add(data);
catch(Exception e)
System.err.println(e);
return elem;
class Myquery
JComboBox com;
public String sendQuery(JComboBox combo)
com = combo;
String collect = combo.getSelectedItem().toString();
return collect;

Answer 1

1. If you post GUI questions to this forum then you are using the wrong forum.
2. If you JDBC code is in the same class as GUI code then you ware coding it wrong.