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i am creating to create a hotel reservation system ,but evey time i run my project i recieve "Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException" and i have not been able to find why . here is the error report i recieve 

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at hotelreservation.Reservation.fill(Reservation.java:389)  at hotelreservation.Reservation.fill(Reservation.java:389)
at hotelreservation.Reservation.<init>(Reservation.java:31)
at hotelreservation.main.jMenuItem1ActionPerformed(main.java:502)
at hotelreservation.main.access$600(main.java:29)
at hotelreservation.main$6.actionPerformed(main.java:277)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

and here is the class 

package hotelreservation;

import java.awt.event.KeyEvent;
//import java.sql.Date;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.Vector;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**

*
 * @author TOSHIBA
 */
public class Reservation extends javax.swing.JInternalFrame {

    /**
     * Creates new form Reservation
     */
public Reservation() {
    initComponents();
  fill();
    //idgenerate();
    username();
    Date date = new Date();
    txt_date.setDate(date);
}

public void username() {
    dbconnection db = new dbconnection();
    try {
        db.connect();
        db.stm = db.con.createStatement();
        db.rs = db.stm.executeQuery("select User_name from Users where Status='Active'");
        while (db.rs.next()) {
            txt_user.setText(db.rs.getString(1));
        }
    } catch (SQLException e) {
        JOptionPane.showMessageDialog(this, e.toString());
    }
}

public void idgenerate() {

    dbconnection db = new dbconnection();
    int IDincrement = 0;
    try {
        db.connect();
        db.stm = db.con.createStatement();

        db.rs = db.stm.executeQuery("select MAX(Res_ID)from Reservation");

        while(db.rs.next()) {
            if (db.rs.first() == false) {
                txt_id.setText("Res000001");
            } else {
                db.rs.last();
                int autoID = db.rs.getInt(1) + 1;
                String no = String.valueOf(autoID);
                int nolong = no.length();
                for (int a = 0; a < 3 - nolong; a++) {
                    no = "0" + no;
                }
                txt_id.setText("Res" + no);

            }
          /* db.rs.next();
            if (db.rs != null) {
                IDincrement = db.rs.getInt(1) + 1;
                IDincrement++;
            } else {
                IDincrement = 1;
            }
            txt_id.setText("CS" + IDincrement);*/
        }

    } catch (SQLException e) {

        JOptionPane.showMessageDialog(this,"Error \n"+ e.getMessage(),"warning",JOptionPane.WARNING_MESSAGE);
    }

}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    jScrollPane1 = new javax.swing.JScrollPane();
    jTable1 = new javax.swing.JTable();
    jPanel3 = new javax.swing.JPanel();
    jButton4 = new javax.swing.JButton();
    jButton1 = new javax.swing.JButton();
    txt_user = new javax.swing.JTextField();
    txt_date = new com.toedter.calendar.JDateChooser();
    jLabel6 = new javax.swing.JLabel();
    jLabel9 = new javax.swing.JLabel();
    jLabel5 = new javax.swing.JLabel();
    txt_rrate = new javax.swing.JTextField();
    txt_rid = new javax.swing.JTextField();
    jLabel4 = new javax.swing.JLabel();
    txt_id = new javax.swing.JTextField();
    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jLabel7 = new javax.swing.JLabel();
    jLabel3 = new javax.swing.JLabel();
    txtlname = new javax.swing.JTextField();
    txt_fname = new javax.swing.JTextField();
    txt_tel = new javax.swing.JTextField();
    filler1 = new javax.swing.Box.Filler(new java.awt.Dimension(0, 0), new java.awt.Dimension(0, 0), new java.awt.Dimension(0, 0));
    jPanel2 = new javax.swing.JPanel();
    jLabel8 = new javax.swing.JLabel();

    setBackground(new java.awt.Color(204, 204, 204));
    setClosable(true);
    setTitle("Reservation Form");
    setFont(new java.awt.Font("Arial", 1, 14)); // NOI18N
    setFrameIcon(new javax.swing.ImageIcon(getClass().getResource("/images/Icon-Edit-Reservations1.png"))); // NOI18N
    setName(""); // NOI18N
    setVisible(false);

    jPanel1.setBackground(new java.awt.Color(255, 204, 51));
    jPanel1.setBorder(new javax.swing.border.SoftBevelBorder(javax.swing.border.BevelBorder.LOWERED, java.awt.Color.black, new java.awt.Color(204, 255, 0), java.awt.Color.red, java.awt.Color.black));

    jScrollPane1.setBackground(new java.awt.Color(255, 204, 51));
    jScrollPane1.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Available Rooms", javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION, javax.swing.border.TitledBorder.DEFAULT_POSITION, new java.awt.Font("Tahoma", 0, 18), new java.awt.Color(204, 0, 204))); // NOI18N
    jScrollPane1.setViewportBorder(javax.swing.BorderFactory.createEtchedBorder(javax.swing.border.EtchedBorder.RAISED, null, java.awt.Color.lightGray));
    jScrollPane1.setAutoscrolls(true);

    jTable1.setBackground(new java.awt.Color(153, 0, 153));
    jTable1.setModel(new javax.swing.table.DefaultTableModel(
        new Object [][] {
            {null, null, null, null},
            {null, null, null, null},
            {null, null, null, null},
            {null, null, null, null}
        },
        new String [] {
            "Room_ID", "Room_Type", "Room_rate", "Status"
        }
    ));
    jTable1.setToolTipText("click on the row you want ");
    jTable1.setGridColor(new java.awt.Color(255, 255, 255));
    jTable1.setSelectionBackground(new java.awt.Color(102, 255, 0));
    jTable1.setSelectionForeground(new java.awt.Color(255, 0, 51));
    jTable1.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseClicked(java.awt.event.MouseEvent evt) {
            jTable1MouseClicked(evt);
        }
    });
    jScrollPane1.setViewportView(jTable1);

    jPanel3.setBackground(new java.awt.Color(255, 204, 51));
    jPanel3.setBorder(javax.swing.BorderFactory.createBevelBorder(javax.swing.border.BevelBorder.LOWERED, new java.awt.Color(204, 0, 204), new java.awt.Color(204, 0, 204), new java.awt.Color(204, 0, 204), new java.awt.Color(204, 0, 204)));

    jButton4.setBackground(new java.awt.Color(204, 0, 204));
    jButton4.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/sav.png"))); // NOI18N
    jButton4.setText("Reserve");
    jButton4.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton4ActionPerformed(evt);
        }
    });

    jButton1.setBackground(new java.awt.Color(204, 0, 204));
    jButton1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/Clear-icon.png"))); // NOI18N
    jButton1.setText("Clear");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    txt_user.setEditable(false);

    txt_date.setDateFormatString("yyyy MMM d");
    txt_date.setEnabled(false);

    jLabel6.setText("Date_In");

    jLabel9.setText("User_name");

    jLabel5.setText("Room_Rate:");

    txt_rrate.setEditable(false);
    txt_rrate.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txt_rrateActionPerformed(evt);
        }
    });
    txt_rrate.addKeyListener(new java.awt.event.KeyAdapter() {
        public void keyPressed(java.awt.event.KeyEvent evt) {
            txt_rrateKeyPressed(evt);
        }
    });

    txt_rid.setEditable(false);

    jLabel4.setText("Room_ID:");

    jLabel1.setText("Res_ID:");

    jLabel2.setText("Firstname:");

    jLabel7.setText("Lastname");

    jLabel3.setText("Telephone:");

    txtlname.addKeyListener(new java.awt.event.KeyAdapter() {
        public void keyTyped(java.awt.event.KeyEvent evt) {
            txtlnameKeyTyped(evt);
        }
    });

    txt_fname.addKeyListener(new java.awt.event.KeyAdapter() {
        public void keyTyped(java.awt.event.KeyEvent evt) {
            txt_fnameKeyTyped(evt);
        }
    });

    txt_tel.setToolTipText(" valid number format +252615178484");
    txt_tel.addKeyListener(new java.awt.event.KeyAdapter() {
        public void keyTyped(java.awt.event.KeyEvent evt) {
            txt_telKeyTyped(evt);
        }
    });

    javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
    jPanel3.setLayout(jPanel3Layout);
    jPanel3Layout.setHorizontalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel3Layout.createSequentialGroup()
            .addGap(18, 18, 18)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                .addGroup(jPanel3Layout.createSequentialGroup()
                    .addComponent(jButton4, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 123, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(175, 175, 175))
                .addGroup(jPanel3Layout.createSequentialGroup()
                    .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(jPanel3Layout.createSequentialGroup()
                            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                .addComponent(jLabel2)
                                .addComponent(jLabel7)
                                .addComponent(jLabel3))
                            .addGap(24, 24, 24)
                            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                .addComponent(txtlname, javax.swing.GroupLayout.DEFAULT_SIZE, 175, Short.MAX_VALUE)
                                .addComponent(txt_id)
                                .addComponent(txt_fname)
                                .addComponent(txt_tel)))
                        .addComponent(jLabel1))
                    .addGap(18, 18, 18)
                    .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jLabel4)
                        .addComponent(jLabel6)
                        .addComponent(jLabel9))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(txt_rid)
                        .addComponent(txt_date, javax.swing.GroupLayout.DEFAULT_SIZE, 155, Short.MAX_VALUE)
                        .addComponent(txt_rrate)
                        .addComponent(txt_user))))
            .addContainerGap(43, Short.MAX_VALUE))
    );
    jPanel3Layout.setVerticalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
            .addContainerGap(40, Short.MAX_VALUE)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(txt_id, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel1)
                .addComponent(txt_rid, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel4))
            .addGap(18, 18, 18)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(txt_fname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel2)
                .addComponent(txt_rrate, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel5))
            .addGap(18, 18, 18)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(txtlname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel7)
                    .addComponent(jLabel6))
                .addComponent(txt_date, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(jLabel9)
                    .addComponent(txt_tel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addComponent(txt_user, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(30, 30, 30)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jButton4, javax.swing.GroupLayout.PREFERRED_SIZE, 31, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 31, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap())
    );

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGap(20, 20, 20)
            .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 0, Short.MAX_VALUE))
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 216, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap(24, Short.MAX_VALUE))
    );

    jPanel2.setBackground(new java.awt.Color(153, 0, 153));

    jLabel8.setFont(new java.awt.Font("Tw Cen MT", 1, 48)); // NOI18N
    jLabel8.setForeground(new java.awt.Color(255, 255, 255));
    jLabel8.setText("Guest Reservation");

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addGap(283, 283, 283)
            .addComponent(jLabel8)
            .addContainerGap(305, Short.MAX_VALUE))
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jLabel8)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(filler1, javax.swing.GroupLayout.PREFERRED_SIZE, 7, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(161, 161, 161))
        .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        .addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(filler1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
    );

    pack();
}// </editor-fold>                        

private void txt_rrateActionPerformed(java.awt.event.ActionEvent evt) {                                          
    // TODO add your handling code here:
}                                         

public void fill() {

    dbconnection db = new dbconnection();
    try {
        db.connect();
        db.stm = db.con.createStatement();
        db.rs = db.stm.executeQuery("select Room_ID,Room_type,Room_Rate,Status from Rooms where Status='Available'ORDER By Room_ID");
        ResultSetMetaData rmetadata = db.rs.getMetaData();
        int columns = rmetadata.getColumnCount();
        DefaultTableModel dtm = new DefaultTableModel();
        Vector columns_name = new Vector();
        Vector data_rows = new Vector();
        for (int i = 1; i <= columns; i++) {
            columns_name.addElement(rmetadata.getColumnName(i));
        }
        dtm.setColumnIdentifiers(columns_name);
        // dtm.setColumnIdentifiers(Columns_name);
        while (db.rs.next()) {
            data_rows = new Vector();
            for (int j = 1; j <= columns; j++) {
                data_rows.addElement(db.rs.getString(j));
            }
            dtm.addRow(data_rows);
        }
        jTable1.setModel(dtm);

    } catch (SQLException e) {
        JOptionPane.showMessageDialog(this, e.getMessage());
    }
}
Abdikair Ømär Møhãmûd
  • 29
  • 1
  • 1
  • 6

2 Answers2

0

It looks like you missed a space in your SQL query just after: whereStatus='Available' in your fill() method.

select Room_ID,Room_type,Room_Rate,Status from Rooms whereStatus='Available'ORDER By Room_ID

Change it to:

select Room_ID,Room_type,Room_Rate,Status from Rooms whereStatus='Available' ORDER By Room_ID.

Since the SQL statement is invalid, db.rs is null resulting in a NullPointerException when db.rs.next() statement is executed.

Itzik Shachar
  • 744
  • 5
  • 16
0

This line

 at hotelreservation.Reservation.fill(Reservation.java:389)

of the stack trace tells that the exception happens in the method fill() at line 389. Null pointer exception basically means that you are calling something on a null object.

Its this line I think 

jTable1.setModel(dtm);

Which means that jTable1 is null. By looking at your code the jTable1 variable that you set earlier in the method initComponents() is local to that specific method which is why it's null on the method fill()

You can fix this by creating class variable jTable1 and using that

Quartal
  • 410
  • 3
  • 14
  • There is really no point in stating the obvious. We have "duplicated" questions for that. – GhostCat May 30 '17 at 18:44
  • can you see that something i'm calling on a null object blease – Abdikair Ømär Møhãmûd May 30 '17 at 18:47
  • @AbdikairØmärMøhãmûd You can find that yourself by looking at line 389 – Quartal May 30 '17 at 18:49
  • @AbdikairØmärMøhãmûd Its this line I think jTable1.setModel(dtm); Which means that jTable1 is null. By looking at your code the jTable1 variable that you set earlier in the method initComponents() is local to that specific method which is why it's null on the method fill() – Quartal May 30 '17 at 18:53
  • @GhostCat i can't se any thing wrong when ever i click on a component in my system like buttons this error shows up – Abdikair Ømär Møhãmûd May 30 '17 at 19:00
  • That is the point: there is no point in discussing anything until you understand what this exception means and how to fix it. Simply Google for npe and Android, you should find a ton of hints how to approach this. – GhostCat May 30 '17 at 19:02