formatting decimal spaces

[Brock Barnes]

Greetings all,
I'm a greenhorn, and I need a little help. I had a little free time at work today and was trying to come up with some example script ideas for practice, and after hearing my wife complain about the credit card bills lastnight, I came up with the one below. Everything in the example works like I wanted/expected, except for the formatting of the double currentTotal. I'm not exactly sure yet how to format the output to where it only displays 2 places after the decimal: $219.79 vs. $219.79255898393723. I've included my sample code and output below (please forgive me...output is long). Any suggestions? Thanks in advance! -Brock
/**********************************************************
* This example should take the total of the credit card,
* add the monthly interest rate to the total and display
* how much you owe at the time of making a payment.
* Then it should subtract the payment and show how much
* you owe after the payment. It should repeat itself until
* you no longer owe anything. It will also show how many
* total months it takes to pay the darn thing off. That is
* provided you don't put anything else on the card like
* dinner at Chili's or Applebee's. =)
***********************************************************/

class CreditCard
{
  public static void main(String[] args)
  {
    double currentTotal = 5000; // Start out with $5,000 maxed on the card
double interestRate = 0.0158; // Anual APR = 19%, so monthly = 1.58%
double payment      = 125; // You make a $125 payment each month

for (int i=0, n=1; i < currentTotal; n++)
{
  // Display current total after interest has been added.
  System.out.println("Month " + n + "\n\t before payment = \t$" +
                    (currentTotal + (currentTotal * interestRate) ) );

  // Calculate current total after interest is added & payment is made
  currentTotal = (currentTotal + ((currentTotal * interestRate) -
                 payment));
 
  // Display current total after interest is added &  payment is made
  // Make sure after payment displays 0 if currentTotal is less than 0.
  
  if (currentTotal > 0)
    {
  System.out.println("\t  after payment = \t$" + currentTotal);
}
else
{
  System.out.println("\t  after payment = \t$0.00");
}
}
  }
}

/* here is the output I get:
C:\jfiles>java CreditCard
Month 1
before payment = $5079.0
after payment = $4954.0
Month 2
before payment = $5032.2732
after payment = $4907.2732
Month 3
before payment = $4984.80811656
after payment = $4859.80811656
Month 4
before payment = $4936.593084801648
after payment = $4811.593084801648
Month 5
before payment = $4887.616255541514
after payment = $4762.616255541514
Month 6
before payment = $4837.86559237907
after payment = $4712.86559237907
Month 7
before payment = $4787.328868738659
after payment = $4662.328868738659
Month 8
before payment = $4735.99366486473
after payment = $4610.99366486473
Month 9
before payment = $4683.847364769593
after payment = $4558.847364769593
Month 10
before payment = $4630.877153132952
after payment = $4505.877153132952
Month 11
before payment = $4577.070012152452
after payment = $4452.070012152452
Month 12
before payment = $4522.412718344461
after payment = $4397.412718344461
*/
edited by Dave to format the code and delete some of the results
[ May 29, 2002: Message edited by: Dave Vick ]

[Dave Vick]

Brock
What you want to look at is the NumberFormat class and its getCurrencyInstance and format methods. You'll get an instance of a NumberFormat object with the getCurrentcyInstance method and then use it to call the format method and pass in the number to be formatted (it is overloaded and can take multiple types of arguments), it'll then return a String with the formatted number.
I added the UBB tags to your post to format your code and also got rid of the other 50 months of results you posted - we got the idea after the first 12
hope that helps

[Brock Barnes]

Well, that points me in the right direction. I'll play around with it and see what I come up with. Thanks for the help.

[Brock Barnes]

Well, that wasn't as bad as I thought it was going to be. Took me a few to find an example of it being used, but I found it in my "Murach's Beginning Java 2" book. You were correct, and it worked perfectly. Thanks a million.
-Brock

  
import java.text.*;
class CreditCard
{
  public static void main(String[] args)
  {
    double currentTotal = 5000; // Start out with $5,000 maxed on the card
double interestRate = 0.0158; // Anual APR = 19%, so monthly = 1.58%
double payment      = 125; // You make a $125 payment each month

for (int i=0, n=1; i < currentTotal; n++)
{
  NumberFormat currency = NumberFormat.getCurrencyInstance();
  String totalInt = currency.format(currentTotal + (currentTotal * interestRate));
  currentTotal = (currentTotal + ((currentTotal * interestRate) - payment));
  String totalIntPay = currency.format(currentTotal);
  // Display current total after interest has been added.  
  System.out.println("Month " + n + "\n\t before payment = \t" +
                    totalInt );
 
  // Display current total after interest is added &  payment is made
  // Make sure after payment displays 0 if currentTotal is less than 0.
  
  if (currentTotal > 0)
    {
  System.out.println("\t  after payment = \t" + totalIntPay);
}
else
{
  System.out.println("\t  after payment = \t$0.00");
}
}
  }
}

and the result:

 
Month 1
         before payment =       $5,079.00
          after payment =       $4,954.00
Month 2
         before payment =       $5,032.27
          after payment =       $4,907.27
Month 3
         before payment =       $4,984.81
          after payment =       $4,859.81
Month 4
         before payment =       $4,936.59
          after payment =       $4,811.59
.....

Month 61
         before payment =       $461.06
          after payment =       $336.06
Month 62
         before payment =       $341.37
          after payment =       $216.37
Month 63
         before payment =       $219.79
          after payment =       $94.79
Month 64
         before payment =       $96.29
          after payment =       $0.00