Question

Need some help on the following problem.

Write a class MortgageCalculator that extends the FinancialCalculator class. The compute method of this class prints out the total interest paid on a mortgage. The monthly payment is computed using this formula:

Monthy payment = Axr/n divided by 1 -[1/(1+r/n)^nT]

where A is the mortgage amount, r is the interest rate, n is the number of payments in a year, and T is the term of the mortgage in years. The total interest paid is calculated by taking the product of the monthly payment, the number of payments in a year n, and the term T. Write a program to test this class.

The FinancialCalculator class:

package inheritance;
import java.util.*;

public abstract class FinancialCalculator {  
// calendar
protected Calendar calendar;

// returns the number of days for the current month set on calendar
protected int getDaysInMonth() {
return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
}

// returns the number of days in the current year set on calendar   
protected int getDaysInYear() {
return calendar.getActualMaximum(Calendar.DAY_OF_YEAR);
}

protected abstract void getUserInput();
protected abstract void compute();
}

Answer 1

package inheritance;

import java.text.DecimalFormat;

import java.util.*;

//Base class FinancialCalculator
abstract class FinancialCalculator {
// calendar
protected Calendar calendar;

// returns the number of days for the current month set on calendar
protected int getDaysInMonth() {
return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
}

// returns the number of days in the current year set on calendar   
protected int getDaysInYear() {
return calendar.getActualMaximum(Calendar.DAY_OF_YEAR);
}
//abstract methods getuser and compute declaration
protected abstract void getUserInput();
protected abstract void compute();

}

//Derived class MortgageCalculator extended from FinancialCalculator
class MortgageCalculator extends FinancialCalculator
{
private static DecimalFormat df2 = new DecimalFormat("#.##");//this is the formate to show only two decimal values after decimal point
  
double A;//the mortgage amount
double r;//the interest rate
double n;//the number of payments in a year
double T;//the term of the mortgage in years
  
  
  
@Override
protected void getUserInput() {//get user methode Definition
Scanner input=new Scanner(System.in);//Scanner class object to get inputs from user
  
System.out.println("\nEnter the Mortgage Amount: ");
A=input.nextDouble();//take Amount from user
  
System.out.println("\nEnter the Interest Rate: ");
r=input.nextDouble();//interest from user
  
System.out.println("\nEnter the Number of Payments in a Year: ");
n=input.nextDouble();//payments in a year in n
  
System.out.println("\nEnter the Term of the Mortgage in Years: ");
T=input.nextDouble();
  
  
compute();//after taking all the inputs from user we will call the compute methode
  
  
}

@Override
protected void compute() {//compute methode definition
  
  

//according to formula's
double Monthy_payment = ((A*r)/n)/(1-(1/(1+r/n)*n)*T);//Calculate payment of month
  
double total_interest_paid= Monthy_payment*n*T;//calculate interest rate
  
  
  
  
System.out.println("\n\nTotal_Interest_Paid: "+df2.format(total_interest_paid));//shows the output as interest rate
  
}
  
}

public class Inheritance {

public static void main(String[] args) {
  
MortgageCalculator object=new MortgageCalculator();//creat MortgageCalculator object to access methods
  
object.getUserInput();//call the userinputs funtion to perform its functionality
  
  
}
  
}

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