Could someone help me with this code??

Question

Hi!, I am really poor at Java, and was given this piece of code to fix. I have no idea why this compiles but does not run and have never dealt with packages either, so I would really appreciate it if someone could tell me what I could do to fix it!!
package Arrays;
import java.awt.*;
import java.awt.event.*;
*   This class demonstrates a simple application
*   A rather primitive ATM machine (needs work)
*   Quite similar to the CashRegister Applet
public class VirtualATM extends Frame implements ActionListener
     // the "screen"
     TextArea  display = new TextArea(8, 20);
     // some local variables
     private String current    = new String("");
     private double amount     = 0d;
     private double balance = 5000.0;
     private int opCode;
     // op code constants
     static final int PINENTRY   = 0;
     static final int DEPOSIT    = 1;
     static final int WITHDRAWAL = 2;
     // button labels - an array
     String [] btnLabels =
         "1", "2", "3", "Deposit",
         "4", "5", "6", "Withdraw",
         "7", "8", "9", "New Customer",
         "0", ".","Enter","Quit"
* Default constructor
public VirtualATM()
     super();
* Constructor with frame title
public VirtualATM(String title)
     super(title);
     setSize(400, 400);
     // inner class to detect window closing and make sure
     // quit method is executed before exit, not vital in
     // this case but a good habit to get into
     addWindowListener(new WindowAdapter()
          public void windowClosing(WindowEvent e)
               quit();
     // set up the display
     int nButtons = btnLabels.length;
     Panel keypad = new Panel();
     keypad.setLayout(new GridLayout(4, 4, 5, 5));
     Button[] keys = new Button[nButtons];
     for (int i = 0; i < nButtons; i++)
          keys[i] = new Button(btnLabels);
          keypad.add(keys[i]);
          keys[i].addActionListener(this);
          keys[i].setActionCommand(btnLabels[i]);
     setLayout(new GridLayout(2, 1, 10, 10));
     display.setEditable(false);
     add(display);
     add(keypad);
     setVisible(true);
     startup();
* Check the button presses
public void actionPerformed(ActionEvent e)
     String command = e.getActionCommand();
     char com = command.charAt(0);
     // see if the character is part of a number:
     if ((com >= '0') && (com <= '9') || (com == '.'))
          doNumber(com);
     else
          // check here for function buttons
          switch (com)
               case 'D' :
               current = "";
                    deposit();
                    break;
               case 'W' :
               current = "";
                    withdraw();
                    break;
               case 'N' :
                    startup();
                    break;
               case 'E' :
                    processOperation();
                    break;
               case 'Q' :
                    quit();
                    break;
* This method prompts for a deposit
public void deposit()
     opCode = DEPOSIT;
     display.append("\nPlease enter amount to deposit: ");
* This method processes number button presses
* Could add PIN validation
public void doNumber(char com)
     current += com;
     if (opCode == PINENTRY)
          display.append("*");
     else
          display.append("" + com);
* This method does the processing!
public void processOperation()
     amount = toDouble(current);
     switch (opCode)
          case PINENTRY :
               display.setText("Please choose a transaction");
               break;
          case DEPOSIT :
               if (amount > 0.0)
                    balance += amount;
                    display.setText("Thank you, your new balance is: " + balance);
               else
                    display.setText("You cannot deposit " + amount);
               break;
          case WITHDRAWAL :
               if (amount <= balance)
                    balance -= amount;
                    display.setText("Thank you, your new balance is: " + balance);
               else
                    display.setText("You cannot withdraw " + amount);
               break;
* This method quits
public void quit()
     System.exit(0);
* This method sets up for a new customer
public void startup()
     display.setText("Welcome to Virtual Banking with VOB\n\n");
     display.append("Please enter your PIN: ");
     amount = 0.0;
     current = "";
     balance = 5000.00;
     opCode = PINENTRY;
* converts a string to a double
private double toDouble(String s)
     double theValue = -1.0;
     try
          if (s != "")
               Double d = new Double(s);
               theValue = d.doubleValue();
     catch (NumberFormatException n)
          current = "";
     finally
          return theValue;
* This method prompts for a withdrawal
public void withdraw()
     opCode = WITHDRAWAL;
     display.append("\nPlease enter amount to withdraw: ");
class main{
     * Initialises the Application
     * Creation date: (07-Dec-00 23:10:49)
     public static void main(String[] args)
          VirtualATM myATM = new VirtualATM("Virtual Overseas Bank");

Answer 1

That sounds like a path or classpath issue issue. There are some instructions here for windows systems...
http://java.sun.com/docs/books/tutorial/getStarted/cupojava/win32.html
Basically you want to set your path to where your java.exe file is.
You can probably run it like this though (if you are in the dir where your ATM class is and you put the path where your jdk is installed):
D:\jdk1.3\bin\java VirtualATM
Here is the code, changed (note that this forum tends to screw up the code a little):
package Arrays;
import java.awt.*;
import java.awt.event.*;
* This class demonstrates a simple application
* A rather primitive ATM machine (needs work)
* Quite similar to the CashRegister Applet
public class VirtualATM extends Frame implements ActionListener
// the "screen"
TextArea display = new TextArea(8, 20);
// some local variables
private String current = new String("");
private double amount = 0d;
private double balance = 5000.0;
private int opCode;
// op code constants
static final int PINENTRY = 0;
static final int DEPOSIT = 1;
static final int WITHDRAWAL = 2;
// button labels - an array
String [] btnLabels =
"1", "2", "3", "Deposit",
"4", "5", "6", "Withdraw",
"7", "8", "9", "New Customer",
"0", ".","Enter","Quit"
* Default constructor
public VirtualATM()
super();
* Constructor with frame title
public VirtualATM(String title)
super(title);
setSize(400, 400);
// inner class to detect window closing and make sure
// quit method is executed before exit, not vital in
// this case but a good habit to get into
addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent e)
quit();
// set up the display
int nButtons = btnLabels.length;
Panel keypad = new Panel();
keypad.setLayout(new GridLayout(4, 4, 5, 5));
Button[] keys = new Button[nButtons];
for (int i = 0; i < nButtons; i++)
keys[i] = new Button(btnLabels);
keypad.add(keys[i]);
keys[i].addActionListener(this);
keys[i].setActionCommand(btnLabels[i]);
setLayout(new GridLayout(2, 1, 10, 10));
display.setEditable(false);
add(display);
add(keypad);
setVisible(true);
startup();
* Check the button presses
public void actionPerformed(ActionEvent e)
String command = e.getActionCommand();
char com = command.charAt(0);
// see if the character is part of a number:
if ((com >= '0') && (com <= '9') || (com == '.'))
doNumber(com);
else
// check here for function buttons
switch (com)
case 'D' :
current = "";
deposit();
break;
case 'W' :
current = "";
withdraw();
break;
case 'N' :
startup();
break;
case 'E' :
processOperation();
break;
case 'Q' :
quit();
break;
* This method prompts for a deposit
public void deposit()
opCode = DEPOSIT;
display.append("\nPlease enter amount to deposit: ");
* This method processes number button presses
* Could add PIN validation
public void doNumber(char com)
current += com;
if (opCode == PINENTRY)
display.append("*");
else
display.append("" + com);
* This method does the processing!
public void processOperation()
amount = toDouble(current);
switch (opCode)
case PINENTRY :
display.setText("Please choose a transaction");
break;
case DEPOSIT :
if (amount > 0.0)
balance += amount;
display.setText("Thank you, your new balance is: " + balance);
else
display.setText("You cannot deposit " + amount);
break;
case WITHDRAWAL :
if (amount <= balance)
balance -= amount;
display.setText("Thank you, your new balance is: " + balance);
else
display.setText("You cannot withdraw " + amount);
break;
* This method quits
public void quit()
System.exit(0);
* This method sets up for a new customer
public void startup()
display.setText("Welcome to Virtual Banking with VOB\n\n");
display.append("Please enter your PIN: ");
amount = 0.0;
current = "";
balance = 5000.00;
opCode = PINENTRY;
* converts a string to a double
private double toDouble(String s)
double theValue = -1.0;
try
if (s != "")
Double d = new Double(s);
theValue = d.doubleValue();
catch (NumberFormatException n)
current = "";
finally
return theValue;
* This method prompts for a withdrawal
public void withdraw()
opCode = WITHDRAWAL;
display.append("\nPlease enter amount to withdraw: ");
* Initialises the Application
* Creation date: (07-Dec-00 23:10:49)
public static void main(String[] args)
VirtualATM myATM = new VirtualATM("Virtual Overseas Bank");