Thread: Program to calculate pay and total sum with daily increment. Urgent!

Hi, i'm working on the last of five programs i need to hand in tonight for an assignment and i'm completely stuck. The instructions are to create a JFrame Form program that calculates the money for someone who has "been hired to a very dangerous job in the amazon rainforest, your pay starts at 0,01 the first day and then doubles to 0,02 next day, then 0,04 etc. How many days must you survive before becoming a millionaire? Create a GUI that shows in a text area how much you make each day. Also show how many days you survived before becoming a millionaire."

I'm supposed to do the calculation using a for loop, or if preferred, a while loop. The relevant part of the code i have at the moment is:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
NumberFormat currency = NumberFormat.getCurrencyInstance();
DecimalFormat pay = new DecimalFormat("0.00");
 
jTextArea1.setText("Day        " + "        Pay" +"\n");
    double amount = 0;
    double initial = 0.01;
    double rate = 1;
 
    // calculate amount on deposit for each of ten years
    for ( double day = 1; amount <= 1000000; day++ )
    {
 
        // calculate new amount for specified day
        amount = initial * Math.pow(1 + rate, day );
        // display the day and the amount
        jTextArea1.append( day + "                      " + pay.format(amount) + "\n");
 
    } // end for
 
}

The output is supposed to start at 0.01 on day 1 like i said, but mine starts at 0.02 and therefore takes one day less than it is supposed to if it was correct. What am i missing here?

Output:

Day                     Pay
1.0                      0,02
2.0                      0,04
3.0                      0,08
4.0                      0,16
5.0                      0,32
6.0                      0,64
7.0                      1,28
8.0                      2,56
9.0                      5,12
10.0                      10,24
11.0                      20,48
12.0                      40,96
13.0                      81,92
14.0                      163,84
15.0                      327,68
16.0                      655,36
17.0                      1310,72
18.0                      2621,44
19.0                      5242,88
20.0                      10485,76
21.0                      20971,52
22.0                      41943,04
23.0                      83886,08
24.0                      167772,16
25.0                      335544,32
26.0                      671088,64
27.0                      1342177,28

What do you expect from?

Math.pow(2,1)

It will return you 2, not 1 as you want, So,

Math.pow(2,0)

will give you your desired result.
Now look into your code. I hope this will help.

Making "day" a global variable and putting this line : jTextArea1.append( day + " " + pay.format(amount) + "\n");
Before the for loop should also fix the problem.

Or an if statement in the loop: if(pay == 0.01)
{
jTextArea1.append( day + " " + pay.format(amount) + "\n");
}

Also, why is "day" a double?

Originally Posted by ppme

Making "day" a global variable and putting this line : jTextArea1.append( day + " " + pay.format(amount) + "\n");
Before the for loop should also fix the problem.

Or an if statement in the loop: if(pay == 0.01)
{
jTextArea1.append( day + " " + pay.format(amount) + "\n");
}

Also, why is "day" a double?

Well, i tried making day a global variable and putting the line "jTextArea1.append( day + " " + pay.format(amount) + "\n");" before the loop and when i do that it only displays one day and the money being 0,00. I also tried putting the if statement in the loop instead, and then i just got the "day" and "pay" words but no numbers whatsoever.

And i changed "day" from a double to an int, that was just some silly mistake.

Originally Posted by ePerKar3

Well, i tried making day a global variable and putting the line "jTextArea1.append( day + " " + pay.format(amount) + "\n");" before the loop and when i do that it only displays one day and the money being 0,00. I also tried putting the if statement in the loop instead, and then i just got the "day" and "pay" words but no numbers whatsoever.

And i changed "day" from a double to an int, that was just some silly mistake.

jTextArea1.append( day + " " + pay.format(amount) + "\n"); Outside and Inside the loop! Sorry should of been more clear

New variable, "total"

total += amount;

total - 1mil > 0
{
tell users earned more than 1 mil
}
amount - 1mil >0
{
tell users more than 1 mil a day
}

Originally Posted by ppme

total - 1mil > 0
{
tell users earned more than 1 mil
}
amount - 1mil >0
{
tell users more than 1 mil a day
}

Thanks a lot for all the help so far. Would you mind elaborating this last one just a little bit though or showing a bit more clearly what you meant? I know i'm being a handful, sorry 'bout that :p

Your "amount" variable holds the amount paid on one particular day. So if you take this amount and minus 1 million form it.. the pay must be greater than 1 million if > 0 holds true.