Computer Science Canada

Need help with my first program
Author:  supahsain08 [ Wed Feb 13, 2008 8:04 pm ]
Post subject:  Need help with my first program
Use code (or syntax) tags! - wtd

Hello, I started java couple of weeks ago, and i know almost nothing about it

My teacher gave us our first java assignment couple of weeks go

We are suppose to make a program which calculate and print out the interest for each month for one year (12 months), then add the interest to the principal to get a new total and print out the new total principle.

My proggy


Java:
class work
{
    public static void main(String[] args)
    {
    double interestrate, principal, interest, time, total;
   
   
   interestrate = 0.12;
   principal = 100.0;
   time = 0.083;
   
   interest = interestrate * principal * time ;
      total = interestrate * principal * time + principal;

int n;
   for (n = 1; n <= 12; n = n +1)
{
   
     System.out.println("The interest for month " + n + " is "+ interest);
       
}
      }
}


the problem is i don't know how to put interest and principle in a for loop too
any hints will be appreciated
Author:  HeavenAgain [ Wed Feb 13, 2008 8:37 pm ]
Post subject:  RE:Need help with my first program
Quote:
put interest and principle in a for loop
just do what you just said, but i dont think "principal" needs to be added in, only the interest and total.........

Ps. your total should only be your interest (for every month) + the initial amount deposit , unless im wrong...
Author:  supahsain08 [ Thu Feb 14, 2008 3:52 pm ]
Post subject:  Re: Need help with my first program
That's my Assignment
This following requirements must be met by the program you write:

Your program should do the following:

* create some variables named interestrate, principal, interest, time, and total (all numbers should be doubles).
* Set the values of the variables interestrate, and principal, to some appropriate numbers (interestrate should be between 0.0 and 1.0)
* Use a for loop to calculate and print out the interest for each month for one year (12 months), then add the interest to the principal to get a new total and print out the new total principle.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Here's my code

code:
import java.text.*;
public class asn1
{
    public static void main(String[] args)
      {
       
       

        double interestrate, principal, interest, time, total;
        int month;
        String pattern1 = "#.##";
        String pattern2 = "###.##";
        DecimalFormat x = new DecimalFormat(pattern1);
        DecimalFormat y = new DecimalFormat(pattern2);
        
        interestrate = 0.12;
        principal = 100;
        time = 0.0833;
        interest = interestrate * principal * time ;

        System.out.println ("Initial Principle = " + principal);
        System.out.println ("Interest Rate = " + interestrate);

        for (month = 1; month <= 12; month = month + 1)
       
{
        interest = interest + 0.01;
        principal = principal + interest;
        System.out.println ("The interest for month " + month + " is " + x.format(interest) + " and the total is " + y.format(principal));

      }
}
}


This is what i don't understand, how am i suppose to calculate the interest each month, i know how to calculate for first month
I = 0.083 * 100 * .12 = 0.996
how do you find the interest for second and third month, what's the formula [/syntax]
Author:  HeavenAgain [ Thu Feb 14, 2008 5:34 pm ]
Post subject:  RE:Need help with my first program
what's the formula?
your teacher just gaved it to you. "interest = principal x rate x time"
in your case, "interest = interestrate * principal * time"
but in your for-loop, you have interest = interest + 0.01; , now what you did is instead of using the equation you have, you just add 0.01 to interest everytime (which is wrong), and after, you have principal = principal + interest; which just says, ok principal just add the interest, which is correct, IF you did your interest correct.

im not sure if you learned a runtime table or whatever it is called, where you follow your code line by line, and put the values in a table, it helps alot when you just begin to learn about loops, do that, and you'll see where you are wrong. (learn to read your own code, and follow it)
Author:  supahsain08 [ Thu Feb 14, 2008 6:08 pm ]
Post subject:  Re: Need help with my first program
K did some more modifications

code:
import java.text.*;

public class asn1
{
  public static void main(String[] args)
   {
     // Declaring Double variables for calculations
     double interestrate, principle, interest, time, total;
     // Declaring int variable for months calculation
     int month;
     // Creating a pattern for outputing desired amount of decimals
     String pattern1 = "#.00";
     String pattern2 = "###.00";
     DecimalFormat x = new DecimalFormat(pattern1);
     DecimalFormat y = new DecimalFormat(pattern2);
     
     // Initializing values for the variables   
     interestrate = 0.120;
     principle = 100.0;
     time = 0.0833;
     interest = interestrate * principle * time ;

     System.out.println ("Initial Principle = " + principle);
     System.out.println ("Interest Rate = " + interestrate);
     
     // Skipping two lines   
     System.out.println("\n");
     System.out.println("\n");
     
     // Using a for loop for months
     for (month = 1; month <= 12; month++)
       
     {
     // Using for loop to calculate principle
     principle = principle + interest;
     // Outputing all the Calculations
     System.out.println ("The interest for month " + month + " is $" +x.format(interest) + " and the new total is $" + y.format(principle));
     // Using for loop to calculate interest
     interest = interestrate * principle * time;
     }
   }
}



Output
Posted Image, might have been reduced in size. Click Image to view fullscreen.

any mistake?
Author:  HeavenAgain [ Thu Feb 14, 2008 6:47 pm ]
Post subject:  RE:Need help with my first program
if i were to be picky about it, your output did not exactly match your teacher's output, the Initial Principle = 100.00 you are missing another 0 on the end, so format that properly, and also
code:
     // Skipping two lines   
     System.out.println("\n");
     System.out.println("\n");
what this does, is not just skip "two" lines, it skiped 4 lines, you have a system.out.println() which already prints 1 line, and in it you are printing another line with "\n"....
Author:  syntax_error [ Thu Feb 14, 2008 6:49 pm ]
Post subject:  RE:Need help with my first program
instead of asking us; do the math on paper first and think; you will answer your own questions that way; be self aware a bit more.

On a side note your class names should have the first letter in CAPS
Author:  supahsain08 [ Thu Feb 14, 2008 7:01 pm ]
Post subject:  RE:Need help with my first program
Thanks HeavenAgain
@ syntax_error: I don't have the first letter in caps because my teacher said file name should be "asn1.java"
Author:  syntax_error [ Thu Feb 14, 2008 7:06 pm ]
Post subject:  RE:Need help with my first program
oo well good coding conventions state: have the first letter of your class in CAPS; jsut keep in as reference for work maybe not for your teacher?

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