Getting index of a string array based on user selection in a comboBox

Question

I'm not really sure how to phrase my questions, but here goes.
I have created a string array that holds the values of a ComboBox. Based on which selection the user makes in the comboBox, I need the program to then perform particular calcualtions (based on their selection). I have tried using an ItemListener, but that doesn't seem to work. I've also tried using the ActionListener connected to the ComboBox, again...without results. I'm not sure what I'm looking for exactly, but I know what I want it to do, I'm just not finding the right way to do it. Can anyone help me figure this out?

Answer 1

Here is my entire code. I'm completely confused at where to put the ActionListener or how to make it do what I want. Right now I just have it set up to display a simple message in the displayArea, just so that I could see if it was working. I think once I figure out how to get the right index from the ComboBox array, then I'll be able to add the code I need to perform the calcualtions...it's just getting to that step that's not going so well! Any help is appreciated.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
import java.lang.String;
public class MortCalcSR5 extends JFrame implements ActionListener
     int term = 0;
     double principal = 0;
     double rate = 0;
     double monthlyPyment = 0;
     double interest = 0;
     String[] loanChoices = {" ", "7 years @ 5.35%", "15 years @ 5.5%", "30 years @ 5.75%"};
     //create panel for input
     JPanel inputPanel = new JPanel();
          JLabel mortAmtLabel = new JLabel("Mortgage Amount $");
          JTextField mortAmtField = new JTextField(15);
          JLabel loanSelectionLabel = new JLabel("Loan Selection");
          JComboBox loanSelection = new JComboBox(loanChoices);
          JTextField loanSelected = new JTextField(15);
     //create button panel
     JPanel buttonPanel = new JPanel();
          JButton calcButton = new JButton("Calculate");
          JButton clearButton = new JButton("Clear");
          JButton exitButton = new JButton("Exit");
     //create panel for payment information
     JPanel paymentPanel = new JPanel();
          JLabel paymentLabel = new JLabel("Monthly Payment $");
          JTextField paymentField = new JTextField(15);
     //create panel for text box information
     JPanel textPanel = new JPanel();
          JLabel numPaymentLabel = new JLabel("Payment #");
          JLabel balLabel = new JLabel("Balance");
          JLabel ytdPrincLabel = new JLabel("Principal");
          JLabel ytdIntLabel = new JLabel("Interest");
     //create payment for display area
     JPanel displayPanel = new JPanel(new FlowLayout());
          JTextArea displayArea = new JTextArea(10,30);
          JScrollPane scroll = new JScrollPane(displayArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
     public MortCalcSR5()
          //set size of GUI display
          setSize(400,450);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          Container pane = getContentPane();
          JScrollPane scroll = new JScrollPane (displayArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
          FlowLayout layout = new FlowLayout(FlowLayout.LEFT);
          pane.setLayout(layout);
          //add components to the inputPanel
          GridLayout layout2 = new GridLayout(4,1);
          inputPanel.setLayout(layout2);
          inputPanel.add(mortAmtLabel);
          inputPanel.add(mortAmtField);
          mortAmtField.setText(" ");
          inputPanel.add(loanSelectionLabel);
          inputPanel.add(loanSelection);
          loanSelection.addActionListener(this);
          pane.add(inputPanel);
          //add components to buttonPanel
          FlowLayout layout3 = new FlowLayout(FlowLayout.CENTER, 10, 10);
          buttonPanel.setLayout(layout3);
          buttonPanel.add(calcButton);
          buttonPanel.add(clearButton);
          buttonPanel.add(exitButton);
          pane.add(buttonPanel);
          //add listeners to buttons
          calcButton.addActionListener(this);
          clearButton.addActionListener(this);
          exitButton.addActionListener(this);
          //add components to outputPanel
          FlowLayout layout4 = new FlowLayout(FlowLayout.LEFT, 10,10);
          paymentPanel.setLayout(layout4);
          paymentPanel.add(paymentLabel);
          paymentPanel.add(paymentField);
          pane.add(paymentPanel);
          //add components to textPanel
          FlowLayout layout5 = new FlowLayout(FlowLayout.LEFT, 10,10);
          textPanel.setLayout(layout5);
          textPanel.add(balLabel);
          textPanel.add(ytdPrincLabel);
          textPanel.add(ytdIntLabel);
          pane.add(textPanel);
          //add components to displayPanel
          FlowLayout layout6 = new FlowLayout(FlowLayout.CENTER,10,10);
          displayPanel.setLayout(layout6);
          displayPanel.add(scroll);
          pane.add(displayPanel);
          setContentPane(pane);
          setVisible(true);
     public void actionPerformed(ActionEvent event)
          String fs = (String)loanSelection.getSelectedItem();
          if (fs.equals("7 years @ 5.35%"))          {
               displayArea.setText("yay");
          else
               displayArea.setText("blah");
          JButton command = (JButton)event.getSource();
          if(command==calcButton)  //calculate button clicked - run payment event
               Payment();
          if(command==clearButton) //clear button clicked - clear all fields
               mortAmtField.setText(null);
               paymentField.setText(null);
               displayArea.setText(null);
               loanSelected.setText(null);  //hidden text field still needs to be cleared
               //loanChoices = null;
          if(command==exitButton)  //exit button clicked - exit program
               System.exit(0);
     public void Payment()
          //perform the calculations
//          int mortAmt = Integer.parseInt(mortAmtField.getText());
     //     double loanSelect = Double.parseDouble((String)loanSelected.getText());
          displayArea.append("Calcualations performed!");
     public static void main(String[] args)
          new MortCalcSR5();
/*/calculations
     int mortAmt = Integer.parseInt(mortAmtField.getText());  //get text user entered in mortAmt field - parse it from a string to integer
     int loanTerm = Integer.parseInt(loanTermField.getText());  //get text user entered in loanTerm field - parse it from a string to integer
     double interestRate = Double.parseDouble(interestRateField.getText());  //get text user entered in interestRate field - parse it from a string to double
     int moTerm = (loanTerm*12);  //calculate monthly loan term
     double moInterest = ((interestRate/100)/12);  //calculate monthly interest rate
     double payment = mortAmt*(moInterest/(1-Math.pow(1/(1+moInterest), moTerm)));  //calculate monthly payment amount
     valid = true;  //number format is accepted
     paymentField.setText(Double.toString(payment));  //display output
*/