Anyone help me? i dunno what's this!!

Question

i am writting code for a simple gui window based java application , and this is the main windows' script:
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
class MenuTest extends JFrame implements ActionListener{
int inc;
Customer customer[];
JMenu mnuAccount, mnuTransaction, mnuHelp;
JMenuItem withdrawalItem, depositItem, balanceItem, newAccountItem,exitItem;
JMenuBar bar;     
JPanel panel, p2, p3, p4;
JLabel JlFirstName, JlLastName,JlBalance, JlID, enqbalance, money, JlDeposit;
JTextField JtFFirstName, JtFLastName, JtFBalance, JtFID, JtFDeposit, JtFWithdraw;
JButton ok, ok2, ok3, ok4, cancel;
public MenuTest(){
     super("Banking Account");
     customer = new Customer [50];
     panel = new JPanel();
     p2 = new JPanel();
p3 = new JPanel();
     p4 = new JPanel();
panel.setVisible(false);     
     p2.setVisible(false);
     p3.setVisible(false);
     p4.setVisible(false);
     inc=0;
     JlFirstName = new JLabel("First Name ");     
     JlLastName = new JLabel("Last Name ");
     JlBalance = new JLabel("Balance ");
     JlID= new JLabel("ID");
enqbalance = new JLabel("");
     JlDeposit = new JLabel("");
     JtFFirstName = new JTextField(50);
     JtFLastName = new JTextField(50);
     JtFBalance = new JTextField(50);
     JtFDeposit = new JTextField(6);
JtFWithdraw = new JTextField(6);
     JtFID = new JTextField(4);
     ok = new JButton("OK");
     ok.addActionListener(this);
     ok2 = new JButton("OK");
     ok2.addActionListener(this);
     ok3 = new JButton("OK");
     ok3.addActionListener(this);
     ok4 = new JButton("Ok");
     ok4.addActionListener(this);     
     cancel = new JButton("Cancel");
     cancel.addActionListener(this);
mnuAccount = new JMenu("Account");
mnuTransaction = new JMenu("Transaction");
     mnuHelp = new JMenu("Help");
     //Set Shortcut key
     mnuAccount.setMnemonic('A');
     mnuTransaction.setMnemonic('T');
     mnuHelp.setMnemonic('H');     
     withdrawalItem = new JMenuItem("Withdrawal");
     depositItem = new JMenuItem("Deposit");
     balanceItem = new JMenuItem("Balance Inquiry");
     newAccountItem = new JMenuItem("New Account");
     exitItem = new JMenuItem("Exit");
//Register the item and menu
     exitItem.addActionListener(this);
     mnuAccount.add(newAccountItem);
     newAccountItem.addActionListener(this);
     mnuAccount.addSeparator();
     mnuAccount.add(exitItem);
     mnuTransaction.add(withdrawalItem);
     withdrawalItem.addActionListener(this);
     mnuTransaction.add(depositItem);
     depositItem.addActionListener(this);
     mnuTransaction.add(balanceItem);     
     balanceItem.addActionListener(this);
     bar = new JMenuBar();
bar.add(mnuAccount);
     bar.add(mnuTransaction);
     bar.add(mnuHelp);
     setJMenuBar(bar);
     setSize(400,400);
     setVisible(true);
public void actionPerformed(ActionEvent e) {
if (e.getSource() == exitItem) {
JOptionPane.showMessageDialog(null,"Press Close On Window Screen To Exit","Help",JOptionPane.PLAIN_MESSAGE);
//ADD NEW ACCOUNT     
else if (e.getSource() == newAccountItem){
     JtFID.setText("");     
panel.setLayout(new GridLayout(5,2));
panel.setSize(400, 400);
     getContentPane().add(panel);
     panel.setVisible(true);
     p2.setVisible(false);
     p3.setVisible(false);
     p4.setVisible(false);
     panel.add(JlFirstName );
     panel.add(JtFFirstName);
     panel.add(JlLastName);
     panel.add( JtFLastName);
     panel.add( JlBalance);
     panel.add( JtFBalance);
     panel.add( JlID);
     panel.add(JtFID);
     panel.add(ok);
     panel.add(cancel);
     panel.setVisible(true);
else if ((e.getSource() == ok) && (emptyID()==true))
     JOptionPane.showMessageDialog(null,"Empty 4-digit ID","Empty ID",JOptionPane.PLAIN_MESSAGE);     
else if ((e.getSource() == ok) && (emptyID()==false))
     Customer c= new Customer(JtFFirstName.getText(), JtFLastName.getText(), JtFID.getText());
     Account account = new Account(Double.parseDouble(JtFBalance.getText()));
     c.setAccount(account);
     customer[inc] = c;
     inc++;
     JOptionPane.showMessageDialog(null,"Add Successful","Adding Customer",JOptionPane.PLAIN_MESSAGE);     
else if (e.getSource() == cancel)
     JtFFirstName.setText("");
     JtFLastName.setText("");
     JtFBalance.setText("");
     JtFID.setText("");
//BALANCE ENQUIRY
else if (e.getSource() == balanceItem)
     JtFID.setText("");
     p2.setLayout(new GridLayout(3,3));
     getContentPane().add(p2);
     panel.setVisible(false);
     p2.add(JlID);
     p2.add(JtFID);
     p2.add(ok2);
     p2.add(enqbalance);
     p4.setVisible(false);
     p3.setVisible(false);
     p2.setVisible(true);
//if ok is press things will be processed     
else if ((e.getSource() == ok2) && (emptyID()==true))
     JOptionPane.showMessageDialog(null,"Empty 4-digit ID","Empty ID",JOptionPane.PLAIN_MESSAGE);     
else if ((e.getSource() == ok2) && (emptyID()==false))
     if(findID(Integer.parseInt(JtFID.getText()))== -1){JOptionPane.showMessageDialog(null,"No such person","Balance Enquiry",JOptionPane.PLAIN_MESSAGE);}
     else
int j = findID(Integer.parseInt(JtFID.getText()));
     enqbalance.setText("First Name=" + customer[j].getFirstName() + "Last Name = " + customer[j].getLastName() + "Balance = " +customer[j].getAccount().getBalance() );      
//DEPOSIT ITEM
else if (e.getSource() ==depositItem)
     JtFID.setText("");
     panel.setVisible(false);
     p2.setVisible(false);
     p4.setVisible(false);
     p3.add(JlID);
     p3.add(JtFID);
     JlDeposit.setText("Deposit amount");
     p3.add(JlDeposit);
     p3.add(JtFDeposit);
     p3.add(ok3);     
     p3.setLayout(new GridLayout(3,3));     
     getContentPane().add(p3);
     p3.setVisible(true);
else if ((e.getSource() == ok3) && (emptyID()==true))
     JOptionPane.showMessageDialog(null,"Empty 4-digit ID","Empty ID",JOptionPane.PLAIN_MESSAGE);     
else if ((e.getSource() == ok3) && (emptyID()==false))
     if(findID(Integer.parseInt(JtFID.getText()))== -1){JOptionPane.showMessageDialog(null,"No such person","Deposit",JOptionPane.PLAIN_MESSAGE);}
     else
     int j = findID(Integer.parseInt(JtFID.getText()));
customer[j].getAccount().deposit(Double.parseDouble(JtFDeposit.getText()));
     JOptionPane.showMessageDialog(null,"Deposit Successful","Deposit",JOptionPane.PLAIN_MESSAGE);     
//WITHDRAWAL
else if (e.getSource() == withdrawalItem)
     JtFID.setText("");
     panel.setVisible(false);
     p2.setVisible(false);
     p3.setVisible(false);
p4.setLayout(new GridLayout(3,3));
     p4.setSize(300,300);
     getContentPane().add(p4);
     p4.add(JlID);
     p4.add(JtFID);
     JlDeposit.setText("Withdrawal");
     p4.add(JlDeposit);
     p4.add(JtFWithdraw);
     p4.add(ok4);     
     p4.setVisible(true);
else if ((e.getSource() == ok4) && (emptyID()) )
     JOptionPane.showMessageDialog(null,"Empty 4-digit ID","Empty ID",JOptionPane.PLAIN_MESSAGE);     
else if( (e.getSource() == ok4) && (!emptyID()) )
     if(findID(Integer.parseInt(JtFID.getText()))== -1){JOptionPane.showMessageDialog(null,"No such person","Withdraw",JOptionPane.PLAIN_MESSAGE);}
     else
     int j = findID(Integer.parseInt(JtFID.getText()));      
customer[j].getAccount().withdraw(Double.parseDouble(JtFWithdraw.getText()));
     JOptionPane.showMessageDialog(null,"Withdrawal Successful","Withdrawal",JOptionPane.PLAIN_MESSAGE);          
public boolean emptyID()
{ if(JtFID.getText()=="")return true;
return false;
public int findID(int id)
for(int i=0; i <=inc; i++)
     if(customer.getID() == Integer.parseInt(JtFID.getText()) )
          return i;
return -1;     
public static void main(String args[]){
MenuTest app = new MenuTest();
app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
when i compile the program and try one of the following:
1) not enter the customer ID and press enter in deposit/withdrawal, the error in the background DOS is like this:
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.
java:48)
at java.lang.Integer.parseInt(Integer.java:489)
at java.lang.Integer.parseInt(Integer.java:518)
at MenuTest.actionPerformed(MenuTest.java:257)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
java.lang.NullPointerException
at MenuTest.findID(MenuTest.java:274)
at MenuTest.actionPerformed(MenuTest.java:257)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
java.lang.NullPointerException
at MenuTest.findID(MenuTest.java:274)
at MenuTest.actionPerformed(MenuTest.java:257)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
anyboydy know how to solve this problem, further more, there's no dialog box pop up saying empty deposit/withdraw messages..please help me!

Answer 1

recently i 've updated my piece of code to handle the NumberFormatException like the below:
     try{       
          Customer2 j = findID(Integer.parseInt(JtFID.getText()));     
String info = "First Name: " + j.getFirstName() + "\nLast Name: " + j.getLastName() + "\nBalance: " +j.getAccount().getBalance() ;
     JOptionPane.showMessageDialog(null,info,"Customer Balance Enquiry",JOptionPane.PLAIN_MESSAGE);          
     enqbalance.setText("");                
catch (NumberFormatException info){JOptionPane.showMessageDialog(null,"No such person /Invalid Data Insertion, please try again!","Balance Enquiry",JOptionPane.PLAIN_MESSAGE);}
but there's still similar error stating me i've got this issue:
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.
java:48)
this are the first few ling of error, how could this happened as i already add the exception handling purpose?