Question

It's not showing anything. I've tried many things but only a small window pops up. Below is my code so far.

It's creating a Mortgage Calculator with GUI. Having user input the principle, term, and rate.

**************************************************************************************************************************

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Mortgage extends JFrame implements ActionListener
{
//declaring components
private JTextField principle, rate, terms, result;
private JButton calculate, reset, exit;
  
  
//constructor
  
public Mortgage()
{
setLayout(new GridLayout(0,2));
//adding labels and textfields
add(new JLabel("Principle:"));
principle = new JTextField();
add(principle);
  
add(new JLabel("Rate:"));
rate = new JTextField();
add(rate);
  
add(new JLabel("Terms:"));
terms = new JTextField();
add(terms);
  
add(new JLabel("Monthly Payment:"));
result = new JTextField();
result.setEditable(false); //set to read-only
add(result);
  
//create buttons and adding action listeners
calculate = new JButton("Calculate Monthly Payments");
calculate.addActionListener(this);
reset = new JButton("Reset");
reset.addActionListener(this);
exit = new JButton("Exit");
exit.addActionListener(this);
  
//create panel and addint buttons
JPanel buttons = new JPanel();
buttons.add(calculate);
buttons.add(reset);
buttons.add(exit);
//adding panel to frame
add(buttons);
//exit on close button
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public static void main(String[] args)
{
new Mortgage();
}
  
public void actionPerformed(ActionEvent e)
{
double loan = Double.parseDouble(principle.getText());
double intRate = Double.parseDouble(rate.getText());
int years = Integer.parseInt(terms.getText());
  
double monthlyInterestRate = getMonthlyInterest(intRate);
double monthlyPayment = getMonthlyPayment(loan, years, monthlyInterestRate);
  
if(e.getSource().equals(reset))
{
principle.setText("");
rate.setText("");
terms.setText("");
result.setText("");
}
else
System.exit(0);
  
}
private double getMonthlyInterest(double intRate)
{
double monthlyInterest = ((intRate / 100) / 12);
return monthlyInterest;
}
private double getMonthlyPayment(double principle, int terms, double rate)
{
double m = terms * 12;
rate = (rate/1200);
  
double monthlyPayment = (principle * rate )/ (1.0 -Math.pow(rate+ 1, -m));
return monthlyPayment;
}
  
  
}
  
  
  
  
  

Answer 1

The code given has missing setSize() method along with some changes have done to show result correctly and changes are documented .

JAVA CODE

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.math.RoundingMode; /* ADDEDD FOR ROUNDING*/
import java.text.DecimalFormat; /* ADDEDD FOR DECIMAL SPACE FORMATTING */

public class Mortgage extends JFrame implements ActionListener
{
   //declaring components
   private JTextField principle, rate, terms, result;
   private JButton calculate, reset, exit;

   //constructor

   public Mortgage()
   {
       setLayout(new GridLayout(0,2));
       //adding labels and textfields
       add(new JLabel("Principle:"));
       principle = new JTextField();
       add(principle);

       add(new JLabel("Rate:"));
       rate = new JTextField();
       add(rate);

       add(new JLabel("Terms:"));
       terms = new JTextField();
       add(terms);

       add(new JLabel("Monthly Payment:"));
       result = new JTextField();
       result.setEditable(false); //set to read-only
       add(result);

       //create buttons and adding action listeners
       calculate = new JButton("Calculate Monthly Payments");
       calculate.addActionListener(this);

       reset = new JButton("Reset");
       reset.addActionListener(this);

       exit = new JButton("Exit");
       exit.addActionListener(this);

       //create panel and addint buttons
       JPanel buttons = new JPanel();
       buttons.add(calculate);
       buttons.add(reset);
       buttons.add(exit);
       //adding panel to frame
       add(buttons);
       //exit on close button
       setDefaultCloseOperation(EXIT_ON_CLOSE);
       setVisible(true);
       setSize(600,400); /* code missed */

   }
   public static void main(String[] args)
   {
       new Mortgage();
   }

   public void actionPerformed(ActionEvent e)
   {

       double loan = Double.parseDouble(principle.getText());
       double intRate = Double.parseDouble(rate.getText());
       int years = Integer.parseInt(terms.getText());

       double monthlyInterestRate = getMonthlyInterest(intRate);
       double monthlyPayment = getMonthlyPayment(loan, years, monthlyInterestRate);

       /* code missed */
       if(e.getSource().equals(calculate)) ///
       {
           DecimalFormat df = new DecimalFormat("0.00");
           result.setText(df.format((monthlyPayment)));
       } /* end */
       else if(e.getSource().equals(reset))
       {
           principle.setText("");
           rate.setText("");
           terms.setText("");
           result.setText("");
       }
       else
           System.exit(0);

   }
   private double getMonthlyInterest(double intRate)
   {
       double monthlyInterest = ((intRate / 100) / 12);
       return monthlyInterest;
   }
   private double getMonthlyPayment(double principle, int terms, double rate)
   {
       double m = terms * 12;
       rate = (rate/1200);

       double monthlyPayment = (principle * rate )/ (1.0 -Math.pow(rate+ 1, -m));
       return monthlyPayment;
   }

}

SCREEN SHOT OF CODE

SCREEN SHOT OUTPUT