combo box

[Rich Wilson]

Can some one tell me what I am doing wrong here? I am trying to enable a listener to select the text from the combo box so I can set the string value from
String [] Irates ={"5.35","5.5","5.75"};
String [] Nyears = {"7","15","30"};

thses strings and assign them to these variables with a loop

double aprnum = Double.parseDouble("0" + apr.getText());
double yearnum = Double.parseDouble("0" + yearsField.getText());

I have read and tried this for the past 10 hours and everytime I get it setup where it will compile and run (I think) the buttons quit working.

http://java.sun.com/docs/books/tutorial/ui...html#uneditable

/*
Modify the mortgage program to allow the user to 
input the amount of a mortgage and then select from 
a menu of mortgage loans: 7 year at 5.35%, 15 year at 5.5 %, and 30 year at 5.75%.  
Use an array for the different loans.  Display the mortgage payment amount. 
Then, list the loan balance and interest paid for each payment over the term of the loan.  
Allow the user to loop back and enter a new amount and make a new selection, or quit.  
Insert comments in the program to document the program.  
Note: This program was written without a graphical user interface in POS406.
*/
 

 
  import java.awt.*;
  import java.awt.event.*;
  import javax.swing.*;
  import java.text.*;
  import javax.swing.JScrollPane;
  import java.awt.BorderLayout;
 
  import javax.swing.text.NumberFormatter;
  import java.text.ParseException;
  import java.text.DecimalFormat;
  import java.net.URL;
 

   public class Darrin_Wilson_week2 extends JFrame
   implements ItemListener,ActionListener {
  
     private boolean focusIsSet = false;
  
     Container pane = getContentPane();
   
  
  
  //row1 
  
     String[] loan = { "","7 years @ 5.35%", "15 years @ 5.5%", "30 years @ 5.75%"};
     String [] Irates ={"5.35","5.5","5.75"};
     String [] Nyears = {"7","15","30"};
     
     
        
     JPanel row1 = new JPanel();
     JComboBox choices = new JComboBox(loan);
     JComboBox petList = new JComboBox(Irates);
  
     
   
     JLabel rate = new JLabel("Loan type", JLabel.LEFT);
     JLabel amount = new JLabel("Amount Financed",JLabel.CENTER);
     JTextField apr = new JTextField (8);
     JTextField amountField = new JTextField (8);
     JTextField yearsField = new JTextField (8);
  
  
  //Table Panel
     JTextField paymentField = new JTextField (8);
     JTextField totalField = new JTextField (8);
     JTextArea DataDisplay = new JTextArea();
    
  
  //row5
     JPanel row5 = new JPanel();
     JButton close = new JButton("Exit");
     JButton start = new JButton("Run");
     JButton clear = new JButton("Reset");
  
  
      public Darrin_Wilson_week2() {
        super("Week 2 mortgage app");
     
        JScrollPane scrollPane = new JScrollPane(DataDisplay);
     
     //button listner
        close.addActionListener(this);
        start.addActionListener(this);
        clear.addActionListener(this);
        choices.addActionListener(this); 
      
        
        
     
       //Create the combo box, select the item at index 4.
       //Indices start at 0, so 4 specifies the pig.
        
        choices.setSelectedIndex(0);
        choices.addActionListener(this);
     
           
     //pane layout
        setSize(650, 250);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container pane = getContentPane();
           
     //row1
        row1.add(rate);
        row1.add(choices);
        row1.add(amount);
        row1.add(amountField);
       
        row1.setBackground(Color.white); 
        row1.setPreferredSize(new Dimension(250, 50));
        pane.add(row1, BorderLayout.PAGE_START);
     
     // Table Panel
     
        scrollPane.setPreferredSize(new Dimension(200, 200));  
        pane.add(scrollPane, BorderLayout.CENTER);    
        DataDisplay.setEditable(false);
        DataDisplay.setBackground(Color.white);
        setContentPane(pane);
              
     //row5
        row5.add (start);
        row5.add (clear);
        row5.add (close);
        row5.setBackground(Color.blue);
        row5.setPreferredSize(new Dimension(200, 50));
        pane.add(row5, BorderLayout.PAGE_END);
              
        setVisible(true);
     
     }
  
  //set focus on reset button
      private void setFocus() {
        if (!focusIsSet) {
           apr.requestFocus();
           focusIsSet = true;
        }
     }
  
  
  
  
      public void actionPerformed(ActionEvent event) {
        String command = event.getActionCommand();
       
     
     //button commands
        if (command == "Reset")
           clearAllFields();
     
        if (command=="Run")
           calculate();
     
        if (command == "Exit")
           close();
      
     
     }
            
  
      void clearAllFields(){
        paymentField.setText(null);
        apr.setText(null);
        yearsField.setText(null);
        amountField.setText(null);
        totalField.setText(null);
        DataDisplay.setText(null);
        apr.requestFocus();
        focusIsSet = true;
     
     }
  
      void close(){ System.exit(-0);}
  
      void calculate() {
              
        DataDisplay.append("Month\tPrincipal\tIntrest\tBalance\n");
        DataDisplay.append("\tPayment\tPayment\n");
        DataDisplay.append("----------------------------------------------------------------------------\n");
     //set text field input to double value
     
        double aprnum = Double.parseDouble("0" + apr.getText());
        double yearnum = Double.parseDouble("0" + yearsField.getText());
        double amtnum = Double.parseDouble("0" + amountField.getText());
     //compute mortgage payment
        double a = aprnum;
        double m = yearnum*12;
        double b=((a/1200)+((a/1200)/(Math.pow((1+(a/1200)),(m))-1)))*amtnum;
     //output payment
        DecimalFormat AmountFormat = new DecimalFormat("$#####0.00");
        String output = AmountFormat.format(b);
     
        paymentField.setText(""+output);
     //compute total of all payments
        double t=b*m;
        output = AmountFormat.format(t);
        totalField.setText(""+output);
      
                    
     }
  
  
  
  
      public void itemStateChanged(ItemEvent event) {
        Object item = event.getItem();
     
     }
  
      public static void main(String[] arguments) {
        Darrin_Wilson_week2 frame = new Darrin_Wilson_week2();
     }
  }
  

[Tim McGuire]

For starters:

1. You need an action listener for the "choices" combo box to see which loan type the user has chosen.

2. years and apr are returning null as you have it written. You don't need to store values in JTextFields such as yearsfield and apr. Get rid of those JTextFields. Then, you don't have to bother converting their text into doubles. you can keep them in memory by giving their value to a variable. This would be done in the action listener for the choices combo box as follows:

choices.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent event) {
                if(choices.getSelectedIndex() == 1){
                    apr = 5.35;
                    years = 30;   
                }
            }
 
        });
 

I don't see any loop in there that would list the balances, so you will need to add that somehow.

[Rich Wilson]

thank you it worked like a champ. I was trying that once before but I was not including it in the correct method.