Event Handling

Hi

I have to do a mortgage program using graphical user interface. The user can input any amount for the principal of the loan and then have three options for a payment plan. The program should display the mortgage payment then list the loan balance and interest paid for each payment over the life of the loan.

I did the code but there is an event error and I cannot seem to understand why the error is there. The code is attached below. Any assistance would be appreciated.

import java.text.*;
import java.awt.*;
import java.io.*;
import java.awt.event.*;
import java.lang.Math.*;
import javax.swing.*;

public class MortgageCalcOptions extends JFrame implements ActionListener{

//Declare variables & loan array and initialize with values
    //Declares the various button, text fields and labels for the calculator.
    
	JButton calculate, clear;       //Declares the calculate and clear data buttons.
	JTextField tmortgamt, tmortgpmt;           //Declares the text field for the mortgage amount.
        JLabel lmortgamt, lmortgage, lmortgpmt, lmortgdetails;     //Declares the label boxes for mortgage amount and mortgage details.
        JRadioButton select7, select15, select30;       //Declares the radio buttons to make term and interest rate selections
        JScrollPane backpanel;       //List of monthly payments and interest paid per month

java.text.DecimalFormat dec = new java.text.DecimalFormat(",###.00");       //Decimal format
        
        
        int[] mortgtrm = {7, 15, 30};   //Initialises the array for the three different years.
	double[] mortgir = {5.35, 5.5, 5.75};   //Initialises the array for the three different interest rates.    
        double mortgamt = Double.parseDouble(tmortgamt.getText());

//Sets constraints on the lay out of the interface of the calculator.
        
          public MortgageCalcOptions() {
			setLayout(new GridBagLayout());
			GridBagConstraints c = new GridBagConstraints();
    
        //Creating, formatting and position and orientation of each component on the calculator interface. 
        //Set the size of the buttons, labels and text fields.
		
                        lmortgamt = new JLabel("Amount   ");
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 0;
                        c.gridy = 0;
                        c.gridwidth = 1;
                        add(lmortgamt, c);
                        
                        tmortgamt = new JTextField(15);
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 1;
                        c.gridy = 0;
                        c.gridwidth = 3;
                        add(tmortgamt, c);
                        
                        lmortgpmt = new JLabel("Payment   ");
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 0;
                        c.gridy = 3;
                        c.gridwidth = 1;
                        add(lmortgpmt, c);
                        
                        tmortgpmt = new JTextField(15);
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 1;
                        c.gridy = 3;
                        c.gridwidth = 3;
                        add(tmortgpmt, c);
                        
                        lmortgage = new JLabel("Mortgage Details    ");
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 0;
                        c.gridy = 4;
                        c.gridwidth = 1;
                        add(lmortgage, c);
            
                        lmortgdetails = new JLabel("");
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 0;
                        c.gridy = 5;
                        c.gridwidth = 1;
                        add(lmortgdetails, c);
                        
                        calculate = new JButton("Calculate");                        
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 1;
                        c.gridy = 6;
                        c.gridwidth = 1;
                        add(calculate, c);
                        
                        clear = new JButton("Clear Data");                        
                        c.fill = GridBagConstraints.HORIZONTAL;
                        c.gridx = 2;
                        c.gridy = 6;
                        c.gridwidth = 1;
                        add(clear, c);
            
                        backpanel = new javax.swing.JScrollPane();
                        backpanel.setPreferredSize(new Dimension(300, 400));
                        backpanel.setVerticalScrollBarPolicy(javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
                        backpanel.setBorder(javax.swing.BorderFactory.createBevelBorder(javax.swing.border.BevelBorder.LOWERED));
		
                        select7 = new JRadioButton("7 Years at 5.35%", false);
                        select7.setActionCommand("sel7");
		
                        select15 = new JRadioButton("15 Years at 5.50%", false);
                        select15.setActionCommand("sel15");
		
                        select30 = new JRadioButton("30 Years at 5.75%", false);
                        select30.setActionCommand("sel30");

ButtonGroup group = new ButtonGroup();      //Create button group
                        group.add(select7);
                        group.add(select15);
                        group.add(select30);

//Creates the event of the buttons calculate and clear data to perform.
        //The calculate button will calculate the mortgage payment and the clear data button will.
        //allow the user to clear the fields and enter new data.
                        
                        event a = new event();
                        calculate.addActionListener(a); 
                        clear.addActionListener(a);
                        
                  }

public void actionPerformed(ActionEvent a) {

for (int i = 0; i < mortgir.length; i++)
{
                // Formula to calculate one month's mortgage payment
                double mortgpmt = (mortgamt * (mortgir[i]/12/100)) / (1-(Math.pow(1/(1+(mortgir[i]/12/100)),(mortgtrm[i]*12))));

// Formula to calculate the total amount paid over life of the loan
                double tottobepd = (mortgtrm[i]*12) * mortgpmt;
         
                // Formula to calculate the total interest paid over life of the loan
                double totinttobepd = tottobepd - mortgamt;
        
                //Declares and builds additional variables for caluclations
                double mortgbal = mortgamt;
                double balance = tottobepd;
                double intbalance = totinttobepd;
                double mortpdsofar = 0.0;
                double intpaidsofar = 0.0;
                double noofpayments = 0;
                double intpdthismth;
        
       
        //When the calculate button is pressed the payment is calculated and shown in the payment field according to the mortgage plan.
        //Also when the clear data button is pressed all fields are set to null.
		
        String arg = event.getActionCommand();
        String op = a.getActionCommand();
        
             
		if(op.equals("Clear Data")) {
			tmortgamt.setText(null);
			tmortgpmt.setText(null);
			}

else if (op.equals("Calculate")) {
                
                        if (arg == "sel7"){
                            double mortgamt = Double.parseDouble(tmortgamt.getText());
                            mortgpmt = (mortgamt * (mortgir[i]/12/100)) / (1-(Math.pow(1/(1+(mortgir[i]/12/100)),(mortgtrm[i]*12))));				
                            tmortgpmt.setText(""+ dec.format(mortgpmt));
                            lmortgdetails = new JLabel("Payment Number\tLoan Balance\t\tInterest");
                            
                            //This will start the loop statement and declares formula for loan balance and interest paid
                                while (balance > 0.0){

}	
                                intpdthismth = mortgbal * (mortgir[i]/12/100);
                                mortgbal = mortgbal - (mortgpmt - intpdthismth);
                                mortpdsofar = mortpdsofar + (mortgpmt - intpdthismth);
                                intbalance = intbalance - intpdthismth;
                                intpaidsofar = intpaidsofar + intpdthismth;
                                balance = balance - mortgpmt;
                                noofpayments = noofpayments + 1;
                   
                                //Displays the loan balance and interest paid
                                lmortgdetails = new JLabel(noofpayments+"\t\t"+"$" + dec.format(balance)+"\t\t"+"$" + dec.format(intpdthismth));
                    
                    }

if (arg == "sel15"){
                            double mortgamt = Double.parseDouble(tmortgamt.getText());
                            mortgpmt = (mortgamt * (mortgir[i]/12/100)) / (1-(Math.pow(1/(1+(mortgir[i]/12/100)),(mortgtrm[i]*12))));	
                            tmortgpmt.setText(""+ dec.format(mortgpmt));
                            lmortgdetails = new JLabel("Payment Number\tLoan Balance\t\tInterest");
                            
                            //This will start the loop statement and declares formula for loan balance and interest paid
                                while (balance > 0.0){

}	
                                intpdthismth = mortgbal * (mortgir[i]/12/100);
                                mortgbal = mortgbal - (mortgpmt - intpdthismth);
                                mortpdsofar = mortpdsofar + (mortgpmt - intpdthismth);
                                intbalance = intbalance - intpdthismth;
                                intpaidsofar = intpaidsofar + intpdthismth;
                                balance = balance - mortgpmt;
                                noofpayments = noofpayments + 1;
                   
                                //Displays the loan balance and interest paid
                                lmortgdetails = new JLabel(noofpayments+"\t\t"+"$" + dec.format(balance)+"\t\t"+"$" + dec.format(intpdthismth));
			
                    }
                   
                        if (arg == "sel30"){
                            double mortgamt = Double.parseDouble(tmortgamt.getText());
                            mortgpmt = (mortgamt * (mortgir[i]/12/100)) / (1-(Math.pow(1/(1+(mortgir[i]/12/100)),(mortgtrm[i]*12))));
                            tmortgpmt.setText(""+ dec.format(tmortgpmt));
                            lmortgdetails = new JLabel("Payment Number\tLoan Balance\t\tInterest");
                            
                            //This will start the loop statement and declares formula for loan balance and interest paid
                                while (balance > 0.0){

}	
                                intpdthismth = mortgbal * (mortgir[i]/12/100);
                                mortgbal = mortgbal - (mortgpmt - intpdthismth);
                                mortpdsofar = mortpdsofar + (mortgpmt - intpdthismth);
                                intbalance = intbalance - intpdthismth;
                                intpaidsofar = intpaidsofar + intpdthismth;
                                balance = balance - mortgpmt;
                                noofpayments = noofpayments + 1;
                   
                                //Displays the loan balance and interest paid
                                lmortgdetails = new JLabel(noofpayments+"\t\t"+"$" + dec.format(balance)+"\t\t"+"$" + dec.format(intpdthismth));

}
                
                }
            }
        }
        
        
public static void main(String args[]) {
      
   //Sets the size of the calculator interface window, as well as set a lable for it.
   //And allows the user to close the window if so desired.
           
           
           MortgageCalcOptions gui = new MortgageCalcOptions();
           gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           gui.setVisible(true);
           gui.setSize(480,600);
           gui.setTitle("Mortgage Calculator");
		
	}
}

I forgot to add the error I am getting when I try to compile it. I am using NetBeans so the errors are already shown before I compile. The error is below:

MortgageCalcOptions.java:131: error: cannot find symbol
event a = new event();
^
symbol: class event
location: class MortgageCalcOptions
MortgageCalcOptions.java:131: error: cannot find symbol
event a = new event();
^
symbol: class event
location: class MortgageCalcOptions
MortgageCalcOptions.java:164: error: cannot find symbol
String arg = event.getActionCommand();
^
symbol: variable event
location: class MortgageCalcOptions
3 errors

Remember that Java is case sensitive - there is no event class but there is an Event class.

And just some feedback - do yourself a favor and name your variables like a human is going to read your code. It doesn't cost anything to name your variables in a way that makes sense - 'a' is far harder to figure out than something like actionListenerEvent.

To help you out in the future, classes generally start with an Uppercase letter. Therefor, whenever you get an error like:

symbol: class event
location: class MortgageCalcOptions
MortgageCalcOptions.java:131: error: cannot find symbol
event a = new event();
^

see that they are talking about "class event". This should tell you that "event" should be "Event".