Hi, ive got a problem adding data to the database from JList. The function allows me to remove data from the database although when i attempt to add data to the database i seem to come across errors, the program seems to add the data to the list and not to the database. I tried the sql statement on another application and it worked fine. The error that occurs is the following: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException (what does this error mean?)

			

			

			import javax.swing.BorderFactory;
			

			import javax.swing.DefaultListModel;
			

			import javax.swing.JButton;
			

			import javax.swing.JFrame;
			

			import javax.swing.JList;
			

			import javax.swing.JOptionPane;
			

			import javax.swing.JPanel;
			

			import javax.swing.JScrollPane;
			

			import javax.swing.JTextField;
			

			import javax.swing.SwingUtilities;
			

			import java.awt.BorderLayout;
			

			import java.awt.event.ActionEvent;
			

			import java.awt.event.ActionListener;
			

			import java.awt.event.MouseAdapter;
			

			import java.awt.event.MouseEvent;
			

			import java.sql.Connection;
			

			import java.sql.DriverManager;
			

			import java.sql.ResultSet;
			

			import java.sql.SQLException;
			

			import java.sql.Statement;
			

			import java.util.Vector;
			

			import java.util.*;
			

			//public Connection conn;
			

			//public Statement stat;
			

			

			public class ListFrame extends JFrame
			

			{
			

			private JPanel backPanel;
			

			private JPanel inputPanel;
			

			private JTextField inputField;
			

			private JPanel buttonPanel;
			

			private JButton removeButton;
			

			private JButton addButton;
			

			private JScrollPane scroller;
			

			private JPanel database;
			

			private JList list;
			

			private DefaultListModel model, model2;
			

			private Connection conn;
			

			private Statement stat;
			

			StringBuffer results = new StringBuffer();
			

			Vector vector1 = new Vector();
			

			String s;
			

			public ListFrame()
			

			{
			

			super("List Frame");
			

			createGUI();
			

			setModel();
			

			setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			

			pack();
			

			setSize(400, 400);
			

			setVisible(true);
			

			}
			

			

			private void setModel()
			

			{
			

			//model = new DefaultListModel();
			

			// connecttodb();
			

			model = new DefaultListModel();
			

			connecttodb();
			

			list.setModel(model);
			

			//connecttodb();
			

			//model.addElement(vector1);
			

			//connecttodb(database);
			

			}
			

			

			private void createGUI()
			

			{
			

			//connecttodb();
			

			

			createScrollerPanel();
			

			createButtonPanel();
			

			createInputPanel();
			

			// connecttodb();
			

			createBackPanel();
			

			

			add(backPanel, BorderLayout.CENTER);
			

			}
			

			

			private void createScrollerPanel()
			

			{
			

			list = new JList(vector1);
			

			list.addMouseListener(
			

			new MouseAdapter()
			

			{
			

			public void mouseClicked(MouseEvent e)
			

			{
			

			listClicked();
			

			}
			

			});
			

			

			scroller = new JScrollPane(list);
			

			

			}
			

			

			private void connecttodb(){
			

			

			try
			

			{
			

			Class.forName("com.mysql.jdbc.Driver");
			

			Connection conn = DriverManager.getConnection("jdbc:mysql:///wordlist", "Username", "Password");
			

			Statement stat = conn.createStatement();
			

			

			ResultSet rs = stat.executeQuery("SELECT * FROM wordlist");
			

			//list.setModel(model);
			

			Vector vector1 = new Vector();
			

			while(rs.next()) vector1.add(rs.getObject(1));
			

			//String s = vector1.toString();
			

			//model.addElement(iter.next());
			

			

			//Looping through vector and adding each individual element to model
			

			ListIterator iter = vector1.listIterator();
			

			while (iter.hasNext()) {
			

			//System.out.println((String)iter.next());
			

			model.addElement(iter.next());
			

			//vector1.add(s);
			

			//model.addElement(vector1.elements());
			

			//vector1.get(i)
			

			}
			

			

			

			//list = new JList(model);
			

			//list.setVisibleRowCount( 9 );
			

			list.repaint();
			

			

			}
			

			catch(SQLException sqlException)
			

			{
			

			JOptionPane.showMessageDialog(null,sqlException.getMessage(),
			

			"Database Error1", JOptionPane.ERROR_MESSAGE);
			

			System.exit(1);
			

			}
			

			

			catch (ClassNotFoundException classNotFound)
			

			{
			

			JOptionPane.showMessageDialog(null, classNotFound.getMessage(),
			

			"Driver Not Found", JOptionPane.ERROR_MESSAGE);
			

			System.exit(1);
			

			

			}
			

			

			

			

			

			}
			

			

			

			

			private void createButtonPanel()
			

			{
			

			addButton = new JButton("Add");
			

			addButton.addActionListener(
			

			new ActionListener()
			

			{
			

			public void actionPerformed(ActionEvent e)
			

			{
			

			addButtonClicked();
			

			}
			

			});
			

			removeButton = new JButton("Remove");
			

			//   removeButton.setEnabled(false);
			

			removeButton.addActionListener(
			

			new ActionListener()
			

			{
			

			public void actionPerformed(ActionEvent e)
			

			{
			

			removeButtonClicked();
			

			}
			

			});
			

			buttonPanel = new JPanel();
			

			buttonPanel.add(addButton);
			

			buttonPanel.add(removeButton);
			

			}
			

			

			private void createInputPanel()
			

			{
			

			inputPanel = new JPanel(new BorderLayout());
			

			inputPanel.setBorder(BorderFactory.createEmptyBorder(3, 3, 3, 3));
			

			inputField = new JTextField();
			

			inputPanel.add(inputField, BorderLayout.NORTH);
			

			inputPanel.add(buttonPanel, BorderLayout.CENTER);
			

			}
			

			

			private void createBackPanel()
			

			{
			

			// connecttodb();
			

			backPanel = new JPanel(new BorderLayout());
			

			backPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
			

			backPanel.add(scroller, BorderLayout.CENTER);
			

			backPanel.add(inputPanel, BorderLayout.SOUTH);
			

			

			}
			

			

			private void addToDatabase(){
			

			

			try {
			

			Statement statement = conn.createStatement();
			

			

			if ( !inputField.getText().equals( "" )  ) {
			

			String query = "INSERT INTO wordlist (" +
			

			"Words" +
			

			") VALUES ('" +
			

			

			

			inputField.getText() + "')";
			

			conn.nativeSQL( query );
			

			statement.executeUpdate( query );
			

			

			}
			

			

			

			}
			

			

			catch ( SQLException sqlex ) {
			

			//        append( sqlex.toString() );
			

			

			}
			

			// inputField.setText("");
			

			//list.repaint();
			

			//list = new JList(vector1);
			

			// connecttodb();
			

			

			}
			

			

			

			private void deleteFromDatabase(){
			

			

			

			try {
			

			

			Class.forName("com.mysql.jdbc.Driver");
			

			conn = DriverManager.getConnection("jdbc:mysql:///wordlist", "Username", "Password");
			

			

			Statement statement = conn.createStatement();
			

			

			String word = inputField.getText();
			

			//        DO SOME SANITY CHECKS ON word HERE!!!
			

			String query = "DELETE FROM wordlist WHERE Words='" + word + "'";
			

			statement.executeUpdate(query);
			

			

			

			//      conn.nativeSQL( query );
			

			statement.executeUpdate(query);
			

			

			}//End try
			

			catch ( SQLException sqlex ) {
			

			System.err.println( sqlex.toString() );
			

			

			return;
			

			}//End catch
			

			catch ( Exception excp ) {
			

			// process remaining Exceptions here
			

			System.err.println( excp.toString(
			

			) );
			

			

			return;
			

			}//End try-catch block
			

			

			//       }//End for loop
			

			

			

			}
			

			

			

			

			

			private void addButtonClicked()
			

			{
			

			//  model.clear();
			

			s = inputField.getText();
			

			if (s.length() > 0)
			

			{
			

			model.addElement(s);
			

			//   s= vector1.toString();
			

			// model.addElement(s);
			

			//  list = new JList(vector1);
			

			//  model.clear();
			

			//  connecttodb();
			

			//addToDatabase();
			

			}
			

			inputField.setText("");
			

			addToDatabase();
			

			

			

			}
			

			

			private void removeButtonClicked()
			

			{
			

			int n = list.getSelectedIndex();
			

			if (!(n
			< 0) || (n > model.size()))
			

			{
			

			model.remove(n);
			

			}
			

			//  removeButton.setEnabled(false);
			

			deleteFromDatabase();
			

			}
			

			

			private void listClicked()
			

			{
			

			int n = list.getSelectedIndex();
			

			if (!(n
			< 0) || (n > model.size()))
			

			{
			

			removeButton.setEnabled(true);
			

			}
			

			

			}
			

			

			public static void main(String[] args)
			

			{
			

			

			SwingUtilities.invokeLater(new Runnable()
			

			{
			

			public void run()
			

			{
			

			new ListFrame();
			

			

			}
			

			});
			

			}
			

			}