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Thread: Having a bit of trouble trying to loop my project.

  1. #1
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    Question Having a bit of trouble trying to loop my project.

    public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
     
            //format number and currency
           NumberFormat NF = NumberFormat.getCurrencyInstance();
           NumberFormat NI = NumberFormat.getNumberInstance();
     
     
            double months = 1;
            double numyears;
            double loanamount;
            double rate;
     
     
     
           //put while statement here
     
            //prompt loan amount
            System.out.print("Enter Loan Amount:");                           
            loanamount = in.nextDouble();
     
            //prompt rate
            System.out.print("Enter Rate:");
             rate = in.nextDouble();
     
             //prompt years
            System.out.print("Enter Number of Years:");
            numyears = in.nextDouble();
     
     
          //calculation monthly
           monthlypay1 = loanamount * rate / (Math.pow(1 + rate, months)) / (Math.pow(1 + rate, months)-1);
     
     
            System.out.println("The Monthly Payment is: $" + monthlypay1);
     
     
            if (monthlypay1 < 0) {
                System.out.print("You need to enter positive numerical data!");}
            else {
                System.out.print("Would you like to continue calculations(y/n)?");
            }
                choice = in.next();
                System.out.println();
                n = False;
                if (choice.equals(n)) {
                }
                }
     
     
     
     
            }

    Basically I am trying to loop this. I've tried adding a while statement
     while (n.equals( n) {
    I've also tried while n == true basically trying to make a while statement to loop the whole thing so that at the end if the user selects "Y" it will loop them back. If the user selects "N" it will break them out the loop. Please help.


  2. #2
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    Default Re: Having a bit of trouble trying to loop my project.

    I recommend do-while loops in these cases. Are you familiar with those?
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  3. #3
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    Default Re: Having a bit of trouble trying to loop my project.

    No sir, For the most part i've just been looking at tutorials on websites but they have not been helping much.

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    Default Re: Having a bit of trouble trying to loop my project.

    Ok. Well a do-while loop works similar to a while loop, except the operation of the while loop is guaranteed to run at least once, and the loop continue condition is determined at the end of each iteration (instead of before, like in the while loop).
    Oracle's tutorial can be found here: The while and do-while Statements (The Java™ Tutorials > Learning the Java Language > Language Basics)
    A simple example of a do-while loop would be like this:
    Scanner in = new Scanner(System.in);
    int repeat = 0; // This will be used in the condition of our loop
    do {
    	System.out.println("Hello");
    	System.out.println("Enter 0 to repeat, or any other number to exit"); // Prompt the user for input
    	repeat = in.nextInt(); // Recieve that input
    } while(repeat==0); // Condition for the loop

    The code in the do block is guarenteed to run at least once. It will only run again if the user enters 0.
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    Ancharius (October 16th, 2013)

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    Default Re: Having a bit of trouble trying to loop my project.

    Ok so basically in my case I can change "int repeat = 0" to be repeat = y;
    and while y.equals(true);?

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    Default Re: Having a bit of trouble trying to loop my project.

    That depends on how your input is working. Does the user enter the String y or n? If so, you need to read that in as a String with the Scanner, and do a comparison like: while(input.equals("y"));
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    Default Re: Having a bit of trouble trying to loop my project.

    Ah ok That was going to be my next question. Thanks a lot!

     
    int repeat = 0;
     
      while (monthlypay1 < 0) {
                System.out.print("You need to enter positive numerical data!");}
            while (monthlypay1 > 0) {
                System.out.print("Would you like to continue calculations(y/n)?");
                choice = in.nextLine();
            }
            while (choice.equals("y")) { //insert loop here.}
    while (choice.equal("n")) { break;}
    Something like that?

  9. #8
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    Default Re: Having a bit of trouble trying to loop my project.

    Close, but not exactly. I assume you wanted those whiles to be if/elses. I also assume you wanted all of your code in your do-while loop. For do-while loops, everything you are looping goes inside of the do-block. There actually is not a block after the while loop (it looks really odd, I know).
    String choice = "";
    do {
            //prompt loan amount
            System.out.print("Enter Loan Amount:");                           
            loanamount = in.nextDouble();
     
            //prompt rate
            System.out.print("Enter Rate:");
             rate = in.nextDouble();
     
             //prompt years
            System.out.print("Enter Number of Years:");
            numyears = in.nextDouble();
     
     
          	//calculation monthly
           	monthlypay1 = loanamount * rate / (Math.pow(1 + rate, months)) / (Math.pow(1 + rate, months)-1);
     
     
            System.out.println("The Monthly Payment is: $" + monthlypay1);
     
    	if (monthlypay1 < 0) {
                System.out.print("You need to enter positive numerical data!");}
            else {
                System.out.print("Would you like to continue calculations(y/n)?");
            }
    	choice = in.nextLine();
    } while(choice.equals("y"));
    NOTE TO NEW PEOPLE LOOKING FOR HELP ON FORUM:

    When asking for help, please follow these guidelines to receive better and more prompt help:
    1. Put your code in Java Tags. To do this, put [highlight=java] before your code and [/highlight] after your code.
    2. Give full details of errors and provide us with as much information about the situation as possible.
    3. Give us an example of what the output should look like when done correctly.

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    Ancharius (October 16th, 2013)

  11. #9
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    Default Re: Having a bit of trouble trying to loop my project.

    Ok I used the code you had as a guideline .

    public class Monthypayment2 {
        private static double monthlypay1;
        private static String choice;
        private static boolean n;
        private static String False;
        private static boolean y;
     
     
     
        /**
         * @param args the command line arguments
         */
        public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
     
            //format number and currency
           NumberFormat NF = NumberFormat.getCurrencyInstance();
           NumberFormat NI = NumberFormat.getNumberInstance();
     
     
            double months = 1;
            double numyears;
            double loanamount;
            double rate;
     
           int repeat = 0;   //condition for loop
     
           do {
     
     
     
            //prompt loan amount
            System.out.print("Enter Loan Amount:");                           
            loanamount = in.nextDouble();
     
            //prompt rate
            System.out.print("Enter Rate:");
             rate = in.nextDouble();
     
             //prompt years
            System.out.print("Enter Number of Years:");
            numyears = in.nextDouble();
     
     
          //calculation monthly
           monthlypay1 = loanamount * rate / (Math.pow(1 + rate, months)) / (Math.pow(1 + rate, months)-1);
     
     
            System.out.println("The Monthly Payment is: $" + monthlypay1);
     
             y = true;
             n = false;
     
            if (monthlypay1 < 0) {
                System.out.print("You need to enter positive numerical data!");}
            else {
                System.out.print("Would you like to continue calculations(y/n)?");
                choice = in.nextLine();
            }
           } while (choice.equals("y"));
     
                    while(choice.equals("n")) {
                break; }
                   }
     
     
                }

    And yea I did wanted if and else statement but one of my friends who tried to help me said I should use do-while loops.

  12. #10
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    Default Re: Having a bit of trouble trying to loop my project.

    Can anyone help me out with the math on here?
     //calculation monthly
           monthlypay1 = loanamount * rate / (Math.pow(1 + rate, months)) / (Math.pow(1 + rate, months)-1);
    Is what I have.. But i'm not getting the correct numbers...
    When i put in loan amount 100000, with a rate of 6%, and a yearly payment of 30 it should be 599.55$

  13. #11
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    Default Re: Having a bit of trouble trying to loop my project.

    The best advice I could give is to break that down into multiple statements based on order of operations and print out each calculation, so you can see where it goes wrong.

    Break it down to something like this:
    double calc1 = loanamount*rate;
    System.out.println(calc1+"");
    double calc2 = Math.pow(1 + rate, months);
    System.out.println(calc2+"");
    double calc3 = Math.pow(1 + rate, months)-1;
    System.out.println(calc3+"");
    double calc4 = calc1/calc2;
    System.out.println(calc4+"");
    monthlypay1 = calc4/calc3;
    NOTE TO NEW PEOPLE LOOKING FOR HELP ON FORUM:

    When asking for help, please follow these guidelines to receive better and more prompt help:
    1. Put your code in Java Tags. To do this, put [highlight=java] before your code and [/highlight] after your code.
    2. Give full details of errors and provide us with as much information about the situation as possible.
    3. Give us an example of what the output should look like when done correctly.

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    Ancharius (October 17th, 2013)

  15. #12
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    Default Re: Having a bit of trouble trying to loop my project.

    I'll try that. Because I noticed every time that I did my math it came out incorrect numbers. When I compare my code to the formula they are the exact same. But maybe that will help Java make the calculations in the correct order. Thanks again!

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