Need help for a newbie problem

Question

I am VERY new to all this Java programming but have really started to enjoy it.
I have two problems with my program that I can not find answers to.
1. I am looking to find out why my code will not select the right answers when I select the first choice in the array. The answer that is delivered turns out to be the 3rd selection. The second and third selection work great, but the first selection always turns out with the thrid answer.
2. I know I need to do better error checking on the user input. At this point I am only checking for correct integer input, but I dont know how to fix or avoid the error for when the user would mistakedly enter letters instead of numbers.
Any hints?
Code to follow... I hope...
No gui allowed for this program.
First time posting so I hope this works and I do it the right way...
import java.text.DecimalFormat;      //To round to 2 decimal places for payment format.
import java.io.*;                          //Allows User to input.
public class Wk5JimP
     //classes for keyboard inputs from user
     public static InputStreamReader reader = new InputStreamReader (System.in);
     public static BufferedReader keyboard = new BufferedReader (reader);
     //main
     public static void main (String[] args) throws IOException
          //Variables
          DecimalFormat decimal = new DecimalFormat("#,##0.00");     //Makes the decimal format for the output
          int appAmount = 200000;                                             //approved loan amount
          short rPay = 0;                                                       //repayment option
          int ps;                                                                 //payment schedule switching variable.
          //Year array and variables
          int yTerm[] = {30, 15, 7,};                                        //Term of the loan in years array
          short rOller2 = 0;                                                  //looping variable for rolling the years
          short rOller3 = 0;                                                  //looping variable for rolling the years
          //Month array and variables
          int mTerm[] = {360, 180, 84,};                                   //Term of the loan in months array
          short rOller = 0;                                                  //looping variable for rolling the months
          short rOller1 = 0;                                                  //looping variable for rolling the months
          //Interest rate array and variables
          double iRate[] = {5.75, 5.50, 5.35,};                              //interest rate array
          int liRate = 0;                                                       //looping variable for interest rate
          int liRate1 = 0;                                                  //looping variable for interest rate
          // Payment array and variables
          double mPayment[] = {
               ((appAmount*(iRate[0]/12/100))/(1-1/Math.pow((1+iRate[0]/12/100), mTerm[0]))),
               ((appAmount*(iRate[1]/12/100))/(1-1/Math.pow((1+iRate[1]/12/100), mTerm[1]))),
               ((appAmount*(iRate[2]/12/100))/(1-1/Math.pow((1+iRate[2]/12/100), mTerm[2])))
                                   };                                             //monthly payment array
          int lPay = 0;                                                       //looping variable for payment incrementation
          int lPay1 = 0;                                                       //looping variable for payment incrementation
          //Dollar amounts into decimal format of two places
          String fappAmount = decimal.format(appAmount);
          //Output to screen for header information
          System.out.println();
          System.out.println("Congratulations!");
          System.out.println("You are approved for a $" + fappAmount + " loan");
          System.out.println("The three repayment options are listed below.\n");
          System.out.println("-------------------------------------------------------------------------");
          System.out.println(" Repayment\t Loan\t\t   Term\t\t  Interest\t  Monthly");
          System.out.println("  Option\tAmount\t       Years   Months\t  Rate \t          Payment");
          System.out.println("-------------------------------------------------------------------------");
          //Begin repayment option loop for calculation
          while (rOller != 3)
                    // if else loop to second and third repayment options
                  if (rOller1 <= 2)
                       // for statement loops last repayment option
                       for (rPay = 1; rPay <=3; rPay++)
                                {mPayment[lPay] = mPayment[lPay1++];
                                 yTerm[rOller2] = yTerm[rOller3++];
                                 mTerm[rOller] = mTerm[rOller1++];
                                 iRate[liRate] = iRate[liRate1++];
                            //Output to screen for numerical repayment option info
                          System.out.println("    " + rPay + "\t    $" + fappAmount + "\t\t " + yTerm[rOller2] + "\t" + mTerm[rOller] + "\t    " + decimal.format(iRate[liRate]) + "% \t$" + decimal.format(mPayment[lPay])+ "\n\n");
                    else
                         //begin payment option selection
                         System.out.println();
                         System.out.println("Which one of the payment schedules would you like to see?\n");
                         System.out.println("Please enter 1 or 2 or 3 to see the payment schedule\nor enter any other number to exit.");
                         ps = Integer.parseInt(keyboard.readLine());
                              switch (ps)
                                        case 1:
                                             System.out.println("\nOption #1\n");
                                             paysched(yTerm[0], appAmount, iRate[0], mPayment[0]);
                                             break;
                                        case 2:
                                             System.out.println("\nOption #2\n\n");
                                             paysched(yTerm[1], appAmount, iRate[1], mPayment[1]);
                                             break;
                                        case 3:
                                             System.out.println("\nOption #3\n\n");
                                             paysched(yTerm[2], appAmount, iRate[2], mPayment[2]);
                                             break;
                                        default:
                                             System.out.println("Thank you!\n\n");
                                             System.exit(0);
                                  }//end switch
               }//end while
          }//end main
                         //payment schedule method
                         public static void paysched(int yTerm, int appAmount, double iRate, double mPayment) throws IOException
                         //Declare variables for looped calculations
                         DecimalFormat decimal = new DecimalFormat("#,##0.00");     //Makes the decimal format for the output
                         double balance = appAmount;
                         double monIRate = iRate / 12;
                         double iPay = 0;
                         double pPay = 0;
                         short pNum = 1;
                         short year = 1;
                         //Header Output to screen for payment schedule
                         System.out.println("-------------------------------------------------------------------------");
                         System.out.println("   Payment \t   Principle\tInterest\tTotal \t\tBalance");
                         System.out.println(" Year  Month\t   Payment\tPayment \tPayment \tRemaining");
                         System.out.println("-------------------------------------------------------------------------");
                         //Loop for shceduled payment calculation for all but the final year
                         do
                                   //Apply the payment
                                   iPay = balance * (monIRate /100);
                                   pPay = mPayment - iPay;
                                   balance = balance - pPay;
                                   //Output to screen for payment information
                                   System.out.println("   " +year+ " \t " +pNum+ " \t  $" +(decimal.format(pPay))+ "\t$" +(decimal.format(iPay))+ "\t      $" +(decimal.format(mPayment))+ "\t     $" +(decimal.format(balance)));
                                   pNum++;
                                   if (pNum % 13 == 0)
                                        System.out.println("Press enter to see the next year payments.");
                                        System.in.read();
                                        System.in.read();
                                        year++;
                                        pNum = 1;
                                        //Output to screen for payment schedule
                                        System.out.println("-------------------------------------------------------------------------");
                                        System.out.println("   Payment \t   Principle\tInterest\tTotal \t\tBalance");
                                        System.out.println(" Year  Month\t   Payment\tPayment \tPayment \tRemaining");
                                        System.out.println("-------------------------------------------------------------------------");
                                        } //end if
                                } //end do
                         while(year < yTerm);
                         //Final Year calculations
                         do
                                   //Apply the payment
                                   iPay = balance * (monIRate /100);
                                   pPay = mPayment - iPay;
                                   balance = balance - pPay;
                                   //Output to screen for payment information
                                   System.out.println("   " +year+ " \t " +pNum+ " \t  $" +(decimal.format(pPay))+ "\t$" +(decimal.format(iPay))+ "\t      $" +(decimal.format(mPayment))+ "\t     $" +(decimal.format(balance)));
                                   pNum++;
                                   if (pNum % 13 == 0)
                                        System.out.println("Please press enter to select and view another payment schedule.");
                                        System.in.read();
                                        System.in.read();
                                        year++;
                                        } //end if
                              }//end do
                         while(year < (yTerm+1));
                    }//end class
}//end classThis is my first post so please be gentle...
Thanks for any help!

Answer 1

When you choose Java to solve the problems, you need to adapt to the power/strategies/methodology that java offers you, and thats the way for solving problems in Java.
Why would you put the entire implementation for calculation inside main method? You could break down the program into smaller methods which could do the calculation bit and then call them in main method.
Anyways the reason that it is calculating for term of 7 years is that
                       // for statement loops last repayment option
                       for (rPay = 1; rPay <=3; rPay++)
                                {mPayment[lPay] = mPayment[lPay1++];
                                 yTerm[rOller2] = yTerm[rOller3++];You are changing the value of the array yTerm[ ]. Hence once the control is out of the for loop the value of y[0]=7,y[1]=7 and y[2]=7.
Solution 1: mark yTerm as final.
Solution 2: set yTerm[0], yTerm[1] back as 30,15 after the for loop.
                  if (rOller1 <= 2)
                       // for statement loops last repayment option
                       for (rPay = 1; rPay <=3; rPay++)
                                {mPayment[lPay] = mPayment[lPay1++];
                                 yTerm[rOller2] = yTerm[rOller3++];
                                 mTerm[rOller] = mTerm[rOller1++];
                                 iRate[liRate] = iRate[liRate1++];
                            //Output to screen for numerical repayment option info
                          System.out.println("    " + rPay + "\t    $" + fappAmount + "\t\t " + yTerm[rOller2] + "\t" + mTerm[rOller] + "\t    " + decimal.format(iRate[liRate]) + "% \t$" + decimal.format(mPayment[lPay])+ "\n\n");
                       yTerm [0]=30;
                       yTerm [1]=15;
                          }Futher the issue is with monthly calculation of pay back amount in switch - case statement.
As you have not provided what the problem is and what is the criteria for calculation of monthly interest or reducing the amount etc. Its not possible (at least for me) to tell you why it would run to negative. Mathematically that is the only thing possible,
Step 1: make those changes in your code. Make changes required to claculate the balance.
Step 2: Execute the new code and
Step 3: Gimme the dukes.
Cheers
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