Thread: Help with run time error

My algorithm method in another class is

public double getFutureValue(int numberOfYears, int numberOfTimes)
{
return principal * Math.pow((1 + interestRate / numberOfTimes), (numberOfYears * numberOfTimes));
}

my other class, main class, is supposed to display the year and balance. I created a loop so that the year will display as to how many years the user inputs, but the balance for every year is the same. I don't know what is wrong. Help pleaseee.

Here is my method in main with the loop:

public void menu3()
{
System.out.println("If you invested " + f.format(principal) + " in a bank account paying "
+ f.format(interestRate) + " for " + numberOfYears + " years, \ncompounded " + numberOfTimes
+ " times per year, then your balance will be:");

invest.setPrincipal(principal);
invest.setInterestRate(interestRate);
System.out.println("Years \tBalance");
System.out.println("----------------");
for(int year = 1; year <= numberOfYears; year++)
{
System.out.println(year + "\t" + f.format(invest.getFutureValue(numberOfYears, numberOfTimes)));
}

}


It displays (if user inputs numberOfYears to 6 and all other info thats unrelated to my question)
year balance
1 $1647.01
2 $1647.01
3 ""
4 ""
5 ""
6 ""

What should I do so that it compounds the value for each time and not just the one year?

What should I do so that it compounds the value for each time an

Do you have the algorithm for computing the value you need?
Can you get it from google?
Given the algorithm, we should be able to show you how to code it in java.

What should I do so that it compounds the value for each time and not just the one year?

Not knowing the algorithm, I can only guess. You must change the value passed to the method each time around the loop or it will always return the same result. So you need to change one of the variables used in the computation to get the correct results. It could be the principal or the year (your current code always passes the total number of years vs the current year)

So even with a loop, I need to pass numberOfYears and numberOfTimes to it every time?

Do they change as the loop goes around? If they stay the same then:
Are they class variables that the called method can see (the variables are in scope)?
If the method can see them, then it could use their values from where it sees them.

Yes it should change. If the user inputs number of years as 10 then it should display values 1-10 in numberOfYears in my algorithm, so:

algorithm -- principal * Math.pow((1 + interestRate / numberOfTimes), (numberOfYears * numberOfTimes));

principal * Math.pow((1 + interestRate / numberOfTimes), (1 * numberOfTimes));
principal * Math.pow((1 + interestRate / numberOfTimes), (2 * numberOfTimes));
principal * Math.pow((1 + interestRate / numberOfTimes), (3 * numberOfTimes));

and so on for how many years they input, in this case 10.

The nbrTimesAround would be the same as the variable though. My method to put the parameters into is invest.getFutureValue(numberOfYears, numberOfTimes). So if I wrote it like you said it would have to be

int numberOfYears = keyboard.nextInt();
for( int i = 1; i < numberOfYears; i++ )
{
System.out.println(year + "\t" + f.format(invest.getFutureValue(numberOfYears, numberOfTimes)));
numberOfYears = numberOfYears + 2*i;
}

But that would keep it going forever

Copy the value to another variable that is not changed in the loop:

int numberOfYears = keyboard.nextInt();
int loopCntrl = numberOfYears; // save in temp loop control variable
for( int i = 1; i < loopCntrl; i++ ) {
  System.out.println(year + "\t" + f.format(invest.getFutureValue(numberOfYears, numberOfTimes)));
  numberOfYears = numberOfYears + 2*i;  // ????WHAT DOES THIS DO?
} // end for(i)

I figured it out. Thanks for your help!