Creating Multiple Windows

Question

Hi,
I am trying to create a java applet that links to multiple windows when clicked. Basically I will have an applet with 2 buttons, one saying "show calculator," the other saying "mortgage." Upon clicking each one, it should open the corresponding window. The way I currently have it setup is first I have written the applet wiht the 2 buttons, right under it I have written the Mortgage application, then under that the calculator application. The problem I have now is that both the Mortgage and calculator applications have a main method, therefore, the filename must be named one of those application names (for example the mortgage is setup as: public class Mortgage; the calculator is setup as: public class calculator-both have different names-so I must save the file as Mortgage.java or Calculator.java), otherwise I will get an error. If I create each application in a different file, and for the button action if I set the corresponding file to
true (eg. mortgage.setVisible(true);) i.e if I click on Morttgage in the applet, will it know to look for the mortgage file in the directory then show it? Or am I misunderstanding this? Please help. Thanks in advance.

Answer 1

Thanks for the response. As s reference , this is what I have so far:
//Button Applet
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.swing.border.TitledBorder;
public class ButtonAppletDemo extends JApplet implements ActionListener
     private JButton jbtCalculator, jbtMortgage;
     //Initialize Applet
     public void init()
          //Create Panel P1 for Button
          JPanel p1 = new JPanel();
          p1.setLayout(new FlowLayout());
          p1.add(jbtCalculator =      new JButton("Simple Calculator"));
          //Create Panel p2 for Button
          JPanel p2 = new JPanel();
          p2.setLayout(new FlowLayout());
          p2.add(jbtMortgage = new JButton("Mortgage"));
          //Add panels to applet
          getContentPane().add(p1, BorderLayout.WEST);
          getContentPane().add(p2, BorderLayout.EAST);
          //Register listeners
          jbtCalculator.addActionListener(this);
          jbtMortgage.addActionListener(this);
     //Handle the button actions
     public void actionPerformed(ActionEvent e)
          if (e.getSource() instanceof JButton)
               if ("Simple Calculator".equals(actionCommand))
               MortgageApplication.setVisible(true);
               else if("Mortgage".equals(actionCommand))
               MenuDemo.setVisible(true);
//Mortgage Application
public class MortgageApplication extends JFrame implements ActionListener
//Declare and create fields for interest rate, year, loan amount, monthly
payment, and total payment
private JTextField jtfAnnualInterestRate = new JTextfield(10);
private JTextField jtfNumOfYears = new JTextfield(10);
private JTextField jtfLoanAmount = new JTextfield(10);
private JTextField jtfMonthlyPayment = new JTextfield(10);
private JTextField jtfAnnualTotalPayment = new JTextfield(10);
//Declare and create a Compute Mortgage Button
private JButton jbtComputeMortgage = new JButton("Compute Mortgage");
//Constructor
public MortgageApplication()
     //Set propertied on the text fields
     jtfMonthlyPayment.setEditable(false);
     jtfTotalPayment.setEditable(false);
     //Right Align text fields
     jtfAnnualInterestRate.setHorizontalAlignment(JTextField.RIGHT);
     jtfNumOfYears.setHorizontalAlignment(JTextField.RIGHT);
     jtfLoanAmount.setHorizontalAlignment(JTextField.RIGHT);
     jtfMonthlyPayment.setHorizontalAlignment(JTextField.RIGHT);
     jtfAnnualTotalPayment.setHorizontalAlignment(JTextField.RIGHT);
     //Panel P1 to hold labels and text fields
     JPanel p1 = new JPanel();
     p1.setLayout(new GridLayout(5,2));
     p1.add(new Label("Interest Rate"));
     p1.add(jtfAnnualInterestRate);
     p1.add(new Label("Years"));
     p1.add(jtfNumOfYears);
     p1.add(new Label("Loan Amount"));
     p1.add(jtfLoanAmount);
     p1.add(new Label("Monthly Payment"));
     p1.add(jtfMonthlyPayment);
     p1.add(new Label("Total Payment"));
     p1.add(jtfTotalPayment);
     p1.setBorder(new TitledBorder("Enter interest rate, year, and loan
amount"));
     //Panel P2 to hold button
     JPanel p2 = new JPanel();
     p2.setLayout(new FlowLayout(FlowLayout.Right));
     p2.add(jbtComputeMortgage);
     //Add the components to the applet
     getContentPane().add(p1, BorderLayout.CENTER);
     getContentPane().add(p2, BorderLayout.SOUTH);
     //Register Listner
     jbtComputeMortgage.addActionListener(this);
//Main Method
public static void main(String[] args)
     MortgageApplication frame = new MortgageApplication();
     frame.setTitle("Mortgage Application");
     frame.setSize(400, 200);
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     frame.setVisible(true);
//Handler for Button
public void actionPerformed(ActionEvent e)
     if(e.getSource() == jbtComputeMortgage)
          //Get values from text fields
          double interest =
(Double.valueOf(jtfAnnualInterestRate.getText())).doubleValue();
          int year = (Integer.valueOf(jtfNumOfYears.getText())).intValue();
          double loan = (Double.valueOf(jtfLoanAmount.getText())).doubleValue();
          //Create a mortgage object
          Mortgage m = new Mortgage(interest, year, loan);
          //Display monthly and total payment
          jtfMonthlyPayment.setText(String.valueOf(m.monthlyPayment()));
          jtfTotalPayment.setText(String.valueOf(m.totalPayment()));
// MenuDemo Application
public class MenuDemo extends JFrame implements ActionListener
// Text fields for Number 1, Number 2, and Result
private JTextField jtfNum1, jtfNum2, jtfResult;
// Buttons "Add", "Subtract", "Multiply" and "Divide"
private JButton jbtAdd, jbtSub, jbtMul, jbtDiv;
// Menu items "Add", "Subtract", "Multiply","Divide" and "Close"
private JMenuItem jmiAdd, jmiSub, jmiMul, jmiDiv, jmiClose;
// Main method
public static void main(String[] args)
MenuDemo frame = new MenuDemo();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
// Default constructor
public MenuDemo()
setTitle("Menu Demo");
// Create menu bar
JMenuBar jmb = new JMenuBar();
// Set menu bar to the frame
setJMenuBar(jmb);
// Add menu "Operation" to menu bar
JMenu operationMenu = new JMenu("Operation");
operationMenu.setMnemonic('O');
jmb.add(operationMenu);
// Add menu "Exit" in menu bar
JMenu exitMenu = new JMenu("Exit");
exitMenu.setMnemonic('E');
jmb.add(exitMenu);
// Add menu items with mnemonics to menu "Operation"
operationMenu.add(jmiAdd= new JMenuItem("Add", 'A'));
operationMenu.add(jmiSub = new JMenuItem("Subtract", 'S'));
operationMenu.add(jmiMul = new JMenuItem("Multiply", 'M'));
operationMenu.add(jmiDiv = new JMenuItem("Divide", 'D'));
exitMenu.add(jmiClose = new JMenuItem("Close", 'C'));
// Set keyboard accelerators
jmiAdd.setAccelerator(
KeyStroke.getKeyStroke(KeyEvent.VK_A, ActionEvent.CTRL_MASK));
jmiSub.setAccelerator(
KeyStroke.getKeyStroke(KeyEvent.VK_S, ActionEvent.CTRL_MASK));
jmiMul.setAccelerator(
KeyStroke.getKeyStroke(KeyEvent.VK_M, ActionEvent.CTRL_MASK));
jmiDiv.setAccelerator(
KeyStroke.getKeyStroke(KeyEvent.VK_D, ActionEvent.CTRL_MASK));
// Panel p1 to hold text fields and labels
JPanel p1 = new JPanel();
p1.setLayout(new FlowLayout());
p1.add(new JLabel("Number 1"));
p1.add(jtfNum1 = new JTextField(3));
p1.add(new JLabel("Number 2"));
p1.add(jtfNum2 = new JTextField(3));
p1.add(new JLabel("Result"));
p1.add(jtfResult = new JTextField(4));
jtfResult.setEditable(false);
// Panel p2 to hold buttons
JPanel p2 = new JPanel();
p2.setLayout(new FlowLayout());
p2.add(jbtAdd = new JButton("Add"));
p2.add(jbtSub = new JButton("Subtract"));
p2.add(jbtMul = new JButton("Multiply"));
p2.add(jbtDiv = new JButton("Divide"));
// Add panels to the frame
getContentPane().setLayout(new BorderLayout());
getContentPane().add(p1, BorderLayout.CENTER);
getContentPane().add(p2, BorderLayout.SOUTH);
// Register listeners
jbtAdd.addActionListener(this);
jbtSub.addActionListener(this);
jbtMul.addActionListener(this);
jbtDiv.addActionListener(this);
jmiAdd.addActionListener(this);
jmiSub.addActionListener(this);
jmiMul.addActionListener(this);
jmiDiv.addActionListener(this);
jmiClose.addActionListener(this);
// Handle ActionEvent from buttons and menu items
public void actionPerformed(ActionEvent e)
String actionCommand = e.getActionCommand();
// Handle button events
if (e.getSource() instanceof JButton)
if ("Add".equals(actionCommand))
calculate('+');
else if ("Subtract".equals(actionCommand))
calculate('-');
else if ("Multiply".equals(actionCommand))
calculate('*');
else if ("Divide".equals(actionCommand))
calculate('/');
else if (e.getSource() instanceof JMenuItem)
// Handle menu item events
if ("Add".equals(actionCommand))
calculate('+');
else if ("Subtract".equals(actionCommand))
calculate('-');
else if ("Multiply".equals(actionCommand))
calculate('*');
else if ("Divide".equals(actionCommand))
calculate('/');
else if ("Close".equals(actionCommand))
System.exit(0);
// Calculate and show the result in jtfResult
private void calculate(char operator)
// Obtain Number 1 and Number 2
int num1 = (Integer.parseInt(jtfNum1.getText().trim()));
int num2 = (Integer.parseInt(jtfNum2.getText().trim()));
int result = 0;
// Perform selected operation
switch (operator) {
case '+': result = num1 + num2;
break;
case '-': result = num1 - num2;
break;
case '*': result = num1 * num2;
break;
case '/': result = num1 / num2;
// Set result in jtfResult
jtfResult.setText(String.valueOf(result));