How can I tell my program to calculate a specific array?

Question

I am supposed to create a program that calculates a mortgage payment based on the user's input of the Loan's Total Principal. I had to add a selection box (combo box), which I did, but now I need to tell my program to calculate the monthly payment based on the user's input of the principal -and- the selection the use chose. However I am not quite sure how to do that. I have created arrays but I am not sure how to tell my program that If the user selects option A, calculate the payment based on option A's info. If it is B, use B's etc.
Any help is greatly appreciated.
Cheers
Here is a portion of my code: public class test extends JApplet implements ActionListener
     // Defining of format information
     JLabel heading = new JLabel("McBride Financial Services \n" + "Mortgage Calculator \n");
     Font newFontOne = new Font("TimesRoman", Font.BOLD, 20);
     Font newFontTwo = new Font("TimesRoman", Font.ITALIC, 16);
     Font newFontThree = new Font("TimesRoman", Font.BOLD, 12);
     Font newFontFour = new Font("TimesRoman", Font.BOLD, 14);
     JButton calculate = new JButton("Calculate");
     JButton exitButton = new JButton("Quit");
     JButton clearButton = new JButton("Clear");
     JLabel instructions = new JLabel("Please Enter the Principal Amount Below");
     JLabel instructions2 = new JLabel("and Select a Loan Type from the Menu");
     // Declaration of variables
     private double principalAmount;
     private JLabel principalLabel = new JLabel("Principal Amount");
     private NumberFormat principalFormat;
     private JTextField enterPrincipal = new JTextField(10);
     private double finalPayment;
     private JLabel finalPaymentLabel = new JLabel("Monthly Payment is: $ ");
     private NumberFormat finalPaymentFormat;
     private JTextField displayFinalPayment = new JTextField(10);
     String [] loanTypes = {"7 Years @ 5.35%", "15 Years @ 5.50%", "30 Years @ 5.75%"};
     JComboBox loanList = new JComboBox(loanTypes);
**This is where my GUI and init would be created (took this code out)
public void actionPerformed(ActionEvent e)
          JComboBox list = (JComboBox)e.getSource();
          String loan = (String)list.getSelectedItem();
          Object source = e.getSource();
          // Outcome of pressing the calculate button
          if (source == calculate)
               if (String = [1])     //See I started to create a nested If's but I didn't know where to go from here
               Double data = (Double)calculatePayment();
               String sourceInput = data.toString();
               displayFinalPayment.setText(sourceInput);
          // Outcome of pressing the clear button
          else if (source == clearButton)
               enterPrincipal.setText("");
               displayFinalPayment.setText("");
               loanList.setSelectedIndex(0);
          // Outcome of pressing the quit button
          else if (source == exitButton)
               System.exit(1);
public double calculatePayment()
               // Declaration of variables
               int i = 0;
               double [] terms = {7, 15, 30};
               double [] interestRates = {5.35, 5.50, 5.75};
               double [] totalPayments = {84, 180, 360};
               double [] loanInterest = {.0535, .0550, .0575};
               double [] periodInterest = {.0045, .0046, .0048};
               // Calling user input needed for the formula to calculate the payments
               String sourceInput1 = enterPrincipal.getText();
               // Parsing the input
               principalAmount = Double.parseDouble(sourceInput1);
               // Formula for calculating the monthly payment
               finalPayment = principalAmount * (periodInterest[i] * Math.pow((1 + periodInterest), totalPayments[i])) / ((Math.pow((1 + periodInterest[i]), totalPayments[i]) - 1));
               // Formatting the monthly payment to round off two decimal places
               DecimalFormat twoDForm = new DecimalFormat("#.##");
               return Double.valueOf(twoDForm.format(finalPayment));

Answer 1

Encephalopathic wrote:
LoveMyAJ wrote:
How do I implement that into my calculations? Like if I used that statement, how would I tell it to get that specific selection and use the appropriate arrays for it?I don't think that you want to add an actionlistener to the combo box. Rather add it to a button and get the info from the fields and combobox when the button has been pushed. As BDLH points out, the objects in the combobox can be smart and know what data they hold. If you do it this way, make sure that you override the object's toString method so that the combobox will display it correctly.Okay I am still fairly new to all of this but I appreciate your guidance. I will look into that.
Thanks again