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Thread: Interest calculator applet

  1. #1
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    Default Interest calculator applet

    Sorry to bother everyone but I'm having an issue trying to find or help myself with the code to implement calculating interest. Basically a user has to be able to input loan amount/interest %/ terms of the loan and loan payments. My issue is the code for calculating the interest. Here is what i have so far.

    import javax.swing.*;
    import java.awt.*;
    import java.text.*;
    import java.awt.event.*;
     
     
    public class SchoolApplet8 extends JApplet implements ActionListener {
     
     
    	double userAmount;
    	double userInterest;
    	double userTerm;
     
     
    	int month = 0;
    	double remainBalance = 0;
    	double interestPayment = 0;
    	double principalPaid = 0;
     
    	JPanel row1;
    	JLabel lblAmount;
    	JTextField txtAmount;
    	JLabel lblInterest;
    	JTextField txtInterest;
    	JLabel lblTerm;
    	JTextField txtTerm;
    	JLabel lblMonthlyPayments;
    	JTextField txtMonthlyPayments;
    	JLabel lblPayment;
    	JTextField txtPayment;
     
    	JPanel row2;
    	JLabel lblHeader;
    	JTextArea txtResults;
    	JScrollPane textPane;
     
     
    	JPanel row3;
    	JButton calculateButton;
    	JButton clearButton;
    	JButton exitButton;
     
     
     
    	public void init()
    	{
     
     
     
    	//Instantiate GUI Components
     
    	// row1
    	row1 = new JPanel();
     
    	lblAmount = new JLabel(" Loan Amount: $", JLabel.LEFT);
    	txtAmount = new JTextField(10);
     
    	lblMonthlyPayments =  new JLabel("Monthly Payments", JLabel.LEFT);
    	txtMonthlyPayments =  new JTextField(6);
     
     
    	lblInterest = new JLabel("Interest Per Period %", JLabel.LEFT);
    	txtInterest = new JTextField(6);
     
    	lblTerm = new JLabel("Term in Years", JLabel.LEFT);
    	txtTerm = new JTextField(6);
     
     
     
    	// TO DO
    	// create a new JLabel and assign it to lblPayment
    	// create a new JTextField(10) and assign it to txtPayment
     
     
     
    	// row2
    	row2 = new JPanel(new BorderLayout());
     
    	String pad = "                             ";
    	lblHeader = new JLabel("Payment #"+pad+"Monthly Payment Amount:"+pad+"Interest Paid:"+pad+"Principal"+pad+"Balance:");
     
    	txtResults = new JTextArea(10, 53);
    	textPane = new JScrollPane(txtResults);
     
     
     
    	//row 3
    	row3 = new JPanel(new GridLayout(1,3,75,1));
     
    	calculateButton = new JButton("Calculate");
    	clearButton = new JButton("Clear");
    	exitButton = new JButton("Exit");
     
     
     
    	//Build GUI
     
    	setSize(600, 250);
     
     
    	row1.add(lblAmount);
    	row1.add(txtAmount);
     
    	row1.add(lblMonthlyPayments);
    	row1.add(txtMonthlyPayments);
     
    	row1.add(lblInterest);
    	row1.add(txtInterest);
     
    	row1.add(lblTerm);
    	row1.add(txtTerm);
     
     
     
     
    	// To DO
    	// add lblPayment & txtPayment to row1
    	// set editable of txtPayment to false: txtPayment.setEditable(false);
    	//
     
     
     
    	textPane.setPreferredSize(new Dimension(610,200));
    	row2.add(lblHeader,BorderLayout.NORTH);
    	row2.add(textPane,BorderLayout.CENTER);
     
     
     
    	//Create Calculate button and add listener
    	calculateButton.addActionListener(this);
    	clearButton.addActionListener(this);
    	exitButton.addActionListener(this);
     
     
     
     
    	row3.add(exitButton);
    	row3.add(clearButton);
    	row3.add(calculateButton);
    	getContentPane().add(row1,BorderLayout.NORTH);
    	getContentPane().add(row2,BorderLayout.CENTER);
    	getContentPane().add(row3,BorderLayout.SOUTH);
     
     
    	}
     
     
     
     
     
    	//Define actions performed for buttons
    	public void actionPerformed(ActionEvent e)
    	{
    		if (e.getSource() == calculateButton)
    		{
     
     
    			double balance = 0;
    			double monthPayment=0;
     
     
     
    			userAmount = Double.parseDouble(txtAmount.getText());
     
    			userInterest = Double.parseDouble(txtInterest.getText());
     
    			userTerm = Double.parseDouble(txtTerm.getText());
     
     
     
    			//formats answer in currency format then to string format for display
    			NumberFormat fmt = NumberFormat.getCurrencyInstance();
    			monthPayment = CalculateMonthlyPayment();
    			String payment = fmt.format(monthPayment);
     
    			// TO DO
    			// Display payment in txtPayment : txtPayment.setText(" "+ payment);
    			//
     
     
     
    			balance = userAmount;
    			month = (int)userTerm * 12;
     
    			for(int index = 1; index <= month ; index++)
    				{
    				interestPayment = balance * (userInterest * .01/12);
    				principalPaid = monthPayment - interestPayment;
    				remainBalance = balance - principalPaid;
     
     
    				txtResults.append(" " + index + "\t\t "+ fmt.format(balance) + "\t\t"
    				+ fmt.format(interestPayment) + "\t\t"  + fmt.format(remainBalance) + "\n");
     
    				balance = remainBalance;
    				}
     
     
    		}
     
    		else if (e.getSource() == clearButton)
    		{
    			txtAmount.setText(null);
    			txtPayment.setText(null);
    			txtResults.setText(null);
    		}
     
    		else if (e.getSource() == exitButton)
    		{
    			System.exit(0);
    		}
    	}
     
     
    	//Mortgage Payment Calculations
    	double CalculateMonthlyPayment()
    	{
     
    		return (userAmount * ((1 + (userInterest*.01)/12)-1) / (1-(Math.pow((1+(userInterest*.01)/12),-(userTerm*12)))));
     
    	}
     
     
     
    }

    Any help would greatly be appreciated Thanks
    Last edited by helloworld922; September 22nd, 2012 at 07:00 PM. Reason: please use [code] tags


  2. #2
    Super Moderator curmudgeon's Avatar
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    Default Re: Simple Applet Troubles

    Quote Originally Posted by bruizer View Post
    Sorry to bother everyone but I'm having an issue trying to find or help myself ...
    @bruizer: I'm not a moderator on this forum, but most forums that I've been involved with frown on a poster hijacking another poster's thread. Your question is important, so why not create a new thread for it and ask it there? If you need to reference this thread, then provide a link to it.

  3. #3
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    Default Re: Simple Applet Troubles

    Well figured it states applet troubles / and creating new threads and clogging up others posting I figured to keep it within the same category or topic / thanks though no worries. I'll just keep trying on my own thx.

  4. #4
    Super Moderator helloworld922's Avatar
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    Default Re: Interest calculator applet

    For future reference, the best course of action when asking a question is a new thread. If you feel the need you can link to the other thread(s) in your thread. I've moved this for you.

    Also, please use code tags to highlight your code:

    [code=java]
    // your code goes here
    [/code]

    This looks like:

    // your code goes here

    You said you're having problems calculating the interest. What kind of problems are you having? Are you getting a compiler error? Incorrect results? The more info you provide the easier it is for us to help you. If you have a compile error, please post the error message.


    p.s.:

    There's no need to apologies about having a question, that's the main purpose of this forum

  5. #5
    Super Moderator Norm's Avatar
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    Default Re: Interest calculator applet

    Also posted at java applet | DaniWeb
    If you don't understand my answer, don't ignore it, ask a question.

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