AWT-EventQueue-0
Hi, very new to java, in need of some help. Started trying to simply add some information to a table in a Access database. Code compiles but when i actually enter information in the text field i created and press the 'write' to databse button i get this error:
- java -
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at DBDemo2.actionPerformed(DBDemo2.java:80)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5488)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3126)
at java.awt.Component.processEvent(Component.java:5253)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1774)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Output completed (43 sec consumed) - Normal Termination
can anyone help. Here is my code:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.sql.*;
public class DBDemo2 extends JFrame implements ActionListener
{
JTextField IPTxt = new JTextField(10);
JButton writeBtn = new JButton("Write");
JButton displayBtn = new JButton("Display");
JLabel IPLbl= new JLabel("IP Address");
Connection UserDB;
Statement myStatement;
public static void main(String[] args) { new DBDemo2(); }
public DBDemo2()
{
setLayout(new BorderLayout());
setSize(300, 300);
setTitle("Database Demo");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel middle = new JPanel();
middle.setLayout(new FlowLayout());
middle.add(IPLbl);
middle.add(IPTxt);
add("West", middle);
setVisible(true);
JPanel bottom = new JPanel();
bottom.setLayout(new FlowLayout());
bottom.add(writeBtn);
bottom.add(displayBtn);
writeBtn.addActionListener(this);
displayBtn.addActionListener(this);
add("South", bottom);
setVisible(true);
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String sourceURL =
"jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ=UserDB.mdb;";
Connection userDB =
DriverManager.getConnection(sourceURL, "admin", "");
Statement myStatement = userDB.createStatement();
}
catch (ClassNotFoundException cnfe){
System.out.println(cnfe);
}
catch (SQLException sqle) {
System.out.println(sqle);
}
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == writeBtn)
{
String i = IPTxt.getText();
if (i.equals(""))
{
JOptionPane.showMessageDialog(this, "One or more fields are blank idiot");
return;
}
String writeString =
"INSERT INTO Users(IP) VALUES('" + i + "')";
try
{
myStatement.executeUpdate(writeString);
IPTxt.setText("");
}
catch (SQLException sqle) {
JOptionPane.showMessageDialog(this, "Duplicate key " + i);
}
}
if (e.getSource() ==displayBtn) {
try
{
ResultSet results = myStatement.executeQuery
("SELECT IP, FROM Users ORDER BY IP");
while (results.next()) {
System.out.print(results.getString(1));
}
results.close();
}
catch (SQLException sqle) {
System.out.println(sqle);
}
}
}
}
