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Problem with loop initialization

Posted on 2004-09-14
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Last Modified: 2010-03-31
I am almost finished with my Java homework, the 'classic' mortgage amortization.  It runs fairly well except I can't figure out how to stop the first month from displaying all zeros.  It should be starting with the data displayed in week 2...

What am I doing wrong?

//Authors Name:  Tom Pitts
//Assignment:    POS 406: Workshop 3              
//Creation Date: September 11, 2004
//Due Date:      September 15, 2004

import java.lang.Math;                  //Import math class
import java.text.DecimalFormat;      //Import decimal formatting class

 class POS406_W3_TRP { //Declare Class
     public static void main(String[] arguments) {
            double rate = .0575;  //Interest rate in decimal format
            double principle = 200000;  //Amount of loan
            double term = 360;      //Term of loan in months
            double monthlyRate = (rate/12);     //Monthly interest rate = .0575/12

            //Loan Overview Output
            System.out.println("Name:         Tom Pitts");
            System.out.println("Assignment:   Workshop 2");
            System.out.println("________________________ \n");
            System.out.println("Principle       : $" + principle);
            System.out.println("Interest Rate   : " + rate * 100 + "%");
            System.out.println("# of Payments   : " + term);

            /*Mortgage Payment Formula provided by Instructor is:
            Principal * rate / ( 1 - (1 + rate)^ -number of payments )*/

            double payments = (principle * monthlyRate) /  (1- Math.pow((1 + monthlyRate), -term));
            DecimalFormat myVar = new DecimalFormat("$###,##0.00");
            String myoutput = myVar.format(payments);
            System.out.println("Monthly Payment : " + myoutput + "\n");
   
      try
      {System.out.println("Press Enter to Continue");
      System.in.read();
      System.in.read();
      }
      catch(Exception error)
      {}
      
            System.out.print("\tPrincipal\tInterest\tLoan\n"); //Amortization Headings
            System.out.println("Months\tPayment\t\tPayment\t\tBalance\n");//Amortization Headings
            int monthCounter=1;  
            double loanBalance=0.0;
            double interestPaid=0.0;
            double principlePayment=0.0;

                  for (;monthCounter <= 360; monthCounter++) { //Intrement monthCounter by 1 each loop
            DecimalFormat balanceVar = new DecimalFormat("$###,##0.00");
            String decimal_Loan_Balance = balanceVar.format(loanBalance);
            String interestPaid_output = balanceVar.format(interestPaid);
            String principlePayment_output = balanceVar.format(principlePayment);

                  if(monthCounter ==1){
                  interestPaid= principle * monthlyRate;
                  loanBalance= principle - (payments - interestPaid);
                                                }
                  else{
                  interestPaid= loanBalance * monthlyRate;
                  loanBalance= loanBalance - (payments - interestPaid);
                                                }
            
            principlePayment = payments - interestPaid;

            System.out.println(monthCounter + "\t" + principlePayment_output + "\t\t"+ interestPaid_output + "\t\t" + decimal_Loan_Balance);

            if(monthCounter % 12==0)

      try
      {System.out.print("Press Enter to Continue");
      System.in.read();
      System.in.read();
      }
      catch(Exception error)
      {}
      }
 }
 }
0
Comment
Question by:nihlcat
  • 3
  • 2
6 Comments
 
LVL 14

Expert Comment

by:sudhakar_koundinya
ID: 12058259
It should be something like this

//Authors Name:  Tom Pitts
//Assignment:    POS 406: Workshop 3              
//Creation Date: September 11, 2004
//Due Date:      September 15, 2004

import java.lang.Math;               //Import math class
import java.text.DecimalFormat;     //Import decimal formatting class

 class POS406_W3_TRP { //Declare Class
     public static void main(String[] arguments) {
          double rate = .0575;  //Interest rate in decimal format
          double principle = 200000;  //Amount of loan
          double term = 360;     //Term of loan in months
          double monthlyRate = (rate/12);     //Monthly interest rate = .0575/12

          //Loan Overview Output
          System.out.println("Name:         Tom Pitts");
          System.out.println("Assignment:   Workshop 2");
          System.out.println("________________________ \n");
          System.out.println("Principle       : $" + principle);
          System.out.println("Interest Rate   : " + rate * 100 + "%");
          System.out.println("# of Payments   : " + term);

          /*Mortgage Payment Formula provided by Instructor is:
          Principal * rate / ( 1 - (1 + rate)^ -number of payments )*/

          double payments = (principle * monthlyRate) /  (1- Math.pow((1 + monthlyRate), -term));
          DecimalFormat myVar = new DecimalFormat("$###,##0.00");
          String myoutput = myVar.format(payments);
          System.out.println("Monthly Payment : " + myoutput + "\n");
   
     try
     {System.out.println("Press Enter to Continue");
     System.in.read();
     System.in.read();
     }
     catch(Exception error)
     {}
     
          System.out.print("\tPrincipal\tInterest\tLoan\n"); //Amortization Headings
          System.out.println("Months\tPayment\t\tPayment\t\tBalance\n");//Amortization Headings
          int monthCounter=1;  
          double loanBalance=0.0;
          double interestPaid=0.0;
          double principlePayment=0.0;

               for (;monthCounter <= 360; monthCounter++) { //Intrement monthCounter by 1 each loop
          DecimalFormat balanceVar = new DecimalFormat("$###,##0.00");
          String decimal_Loan_Balance = balanceVar.format(loanBalance);
          String interestPaid_output = balanceVar.format(interestPaid);
          String principlePayment_output = balanceVar.format(principlePayment);

               if(monthCounter ==1){
               interestPaid= principle * monthlyRate;
               loanBalance= principle - (payments - interestPaid);
                                        }
               else{
               interestPaid= loanBalance * monthlyRate;
               loanBalance= loanBalance - (payments - interestPaid);
                                        }
         
          principlePayment = payments - interestPaid;
      if(monthCounter >1)
          System.out.println((monthCounter-1) + "\t" + principlePayment_output + "\t\t"+ interestPaid_output + "\t\t" + decimal_Loan_Balance);

          if((monthCounter-1) % 12==0)

     try
     {System.out.print("Press Enter to Continue");
     System.in.read();
     System.in.read();
     }
     catch(Exception error)
     {}
     }
 }
 }
0
 
LVL 14

Accepted Solution

by:
sudhakar_koundinya earned 1000 total points
ID: 12058286
Small correction

>>for (;monthCounter <= 360; monthCounter++) { //Intrement monthCounter by 1 each loop

for (;monthCounter <= 361; monthCounter++) { //Intrement monthCounter by 1 each loop

0
 
LVL 7

Expert Comment

by:bvanderveen
ID: 12058329
Look at where you format interestPaid_output and principlePayment_output - before you compute the source values.
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LVL 7

Expert Comment

by:bvanderveen
ID: 12058353
Just to be clear - step through with Eclipse debugger.  You are computing the payment and interest correctly, but you have already computed principlePayment_output and interestPaid_output from the values of interest and principle as they were initialized (zero).  Just need to move a few lines...

I wish other homework questions were like this - honest, and looking for debugging help, rather than "do it for me".
0
 
LVL 7

Expert Comment

by:bvanderveen
ID: 12060055
Sudhakar's solution works, but I think it is a kludge.  Instead of printing out.

   System.out.println((monthCounter-1) + "\t" + principlePayment_output + "\t\t"+ interestPaid_output + "\t\t" + decimal_Loan_Balance);

You should move the assignments for those variables after interestPaid and loan_balance have been computed.  Then your program will be more "rational".  

Follow the logic - your teacher should give some points off for this crude workaround - it would be harder to maintain and understand.
0
 
LVL 6

Author Comment

by:nihlcat
ID: 12064712
Ok, understood.  I haven't turned it in yet, so I will review this.  I wanted to clean up the code anyway.  THANK YOU for your opinions!
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