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Calculating discount factor in java

I am trying to calculate monthly loan payments the formula Loan Payment = Amount / Discount Factor on www.thebalance.com
According to the website discount factor is calculated with this formula (D) = {[(1 + i) ^n] - 1} / [i(1 + i)^n] I tried interpreting this into Java and came up with
double discountFactor = (Math.pow((1 + interest), numberOfPayments) - 1) / Math.pow(interest * (1 + interest), numberOfPayments);
But it outputs infinityam not so good with Math, can someone help point out the issue?

double discountFactor = (Math.pow((1 + interest), numberOfPayments) - 1) /
(interest * Math.pow((1 + interest), numberOfPayments));
interest is not part of the power, it should be outside power.

put the 'interest' outside the second power function not inside.
double discountFactor = (Math.pow((1 + interest),numberOfPayments)-1)/(interest*Math.pow((1+interest),numberOfPayments));

Calculating Loan Interest and Duration of loan. Java

The following 2 methods are intended to calculate the length of loan(number of monthly payments that have to be paid and the interest due in the loan, respectively, given the parameters in which r is the monthly interest rate(APR), A is the loan amount(principal), P is the monthly payment and N is the number of payments that need to be made. However neither of the methods calculate correctly. How do I fix them so that they provide the number of months the payment must be made and the interest accrued?
public static double loanLength(double r, double A, double P){
double N = (Math.log(1 / (1 - ((r * A) / P)))) / Math.log(1 + r);
return N;
}
public static double loanInterest(double P, double N, double A){
double I = ((P * N) - A);
return I;
}

According to your example input it's just an arithmetic error.
The line double N = (Math.log(1 / (1 - ((r * A) / P)))) / Math.log(1 + r); has some calculations in it. The one that fails (or results in NaN) is Math.log(1 / (1 - ((r * A) / P))).
If we insert the example values: Math.log(1 / (1 - ((0.1 * 10000) / 500))) and we calculate that out:
1. Math.log(1 / (1 - ((0.1 * 10000) / 500)))
2. Math.log(1 / (1 - (1000 / 500)))
3. Math.log(1 / (1 - 2))
4. Math.log(1 / -1)
5. Math.log(-1) // <-- here happens the error
A logarithm of a number smaller/equals than 0 is not defined. So your equation is wrong

This site explains that the interest rate and payment have to be for the same period.
I guess in your case 10% is per year, while 500 is per month. So you need to divide 10 or multiply 500 by 12 to make them fit together. Otherwise, your calculation will give you the duration for a loan with 10%/500payment per month or per year (or any duration really), which can never be payed back: in every period there is 1000 interest, but only 500 payment.
Hence, log(-x) produces NaN, meaning you can never pay back.

Monthly payment calculator returning wrong payment

I am supposed to make a monthly payment calculator in java with the given formula.
The formula for me to use is
M = P * i/ 1 - (1+i)^-n
where
P is the loan principal (i.e. the amount borrowed)
i is monthly interest rate (annual_interest_rate / 12; expressed as decimal)
N is time (number of monthly payments in total years of loan; i.e. years * 12)
The code below is my attempted function to get the monthly payment.
But if I put in 6 years with a loan amount of 200, I get 140 using the formula.
I am stumped as to why I get that number. Any help would be appreciated
public static int calMonthlyPay(double loanAmt, int y) {
double m = 0.0, interest = 0.0, annualIRate = 0.0;
double months = 0.0;
months = y * 12;
annualIRate = getAnnualIRate(y);
interest = annualIRate / 12;
System.out.println(interest);
System.out.println(months);
System.out.println(loanAmt);
System.out.println(y);
m = (loanAmt * (interest - Math.pow((1 + interest), -months))); // This is my formula calculation
System.out.println(m);
return 0;
}
private static double getAnnualIRate(int y) {
switch (y) {
case 2:
return 5.7;
case 3:
return 6.2;
case 4:
return 6.8;
case 5:
return 7.5;
case 6:
return 8.4;
default:
return 8.4;
}
}

If I understood your formula right, it should be:
m = loanAmt * interest - Math.pow(1 + interest, -months);

What you have now is :
m = (loanAmt * (interest / 1 - Math.pow((1 + interest), -months))) =
(loanAmt * (interest - Math.pow((1 + interest), -months)))
You should use the parentheses correctly :
m = loanAmt * (interest / (1 - Math.pow(1 + interest, -months)));

Your formula is incorrect, it need to be
loanAmt * (interest / (1 - Math.pow (1 + interest, -months)));
And there's a error in interest value formula, it need to be
interest = annualIRate / 100 / 12;
So your method calMonthlyPay(200, 6) gives 3 now, which is correct.

Java Calculation Mistake

I am trying to create a program that calculates the futureValue that is in the following formula
futureValue = investmentAmount × (1 + monthlyInterestRate)^years×12
It is a visual program and it calculates the futureValue.Variables: investmentAmount monthlyInterestRate and years are taken from textfields.Here my code is like this
public void Calculator(){
double x = (Double.parseDouble(AnnualInterestRate.getText())/12) + 1;
double y = Double.parseDouble(Years.getText()) * 12;
double mult = Math.pow(x, y);
double futureValue = Double.parseDouble(InvesmentAmount.getText()) * mult;
lblNewLabel_3.setText("$" + String.format("%.2f",futureValue));
}
for these values:
InvesmentAmount : 1000
Years : 2
AnnualInterestRate : 6.5
futureValue should be 1,138.43 but futureValue that is calculated by my program is 32491635,80
I can't see the mistake and It would be great if anybody could help.

If your user is supposed to be inputting the interest rate as a percentage, you need to divide it by 100 as part of your calculation. E.g.
double x = (Double.parseDouble(AnnualInterestRate.getText())/1200) + 1;
Output: $1138.43

Need help porting this equation to java

I'm trying to make a program that calculates the required score to level in a game and the equation works fine on my calculator but not when i try changing it to work with java.
the equation is 5,000 / 3 * (4n^3 - 3n^2 - n) + 1.25 * 1.8^(n - 60) for example level 49 you should need to have a total score of 772240000 points and the calculator gives this answer but my java program doesn't. here is the code i tried.
for (int i = 0; i <= 100; i++) {
double score = (double) ((5000 / 3) * (Math.pow(4 * i, 3) - Math.pow(3 * i, 2) - i) + (1.25 * Math.pow(1.8, i - 60)));
System.out.println("Level " + i + " requires " + (long) score);
}
This doesnt seem to work right and gives 12513130000 as the required points for lvl 49. If anyone can get it to work would you miind explaining what i did wrong.

You're messing up your Math.pow calls, but you can avoid some of them entirely:
double score = (double) ((5000 / 3) * (4 * i * i * i - 3 * i * i - i) + (1.25 * Math.pow(1.8, i - 60)));
Here's what's wrong: Math.pow(4 * i, 3) is actually (4i)^3 and not 4(i^3). To do the latter, you would need the following:
4 * Math.pow(i, 3)
I'm not entirely sure about the integer division part (you are casting it to double), but you may have to change 5000 / 3 to 5000.0 / 3.

Your problem is inside Math.pow - you're multiplying your index value by a scalar each time.
4 * Math.pow(i, 3)
And
3 * Math.pow(i, 2)
Should fix it.
Edit: And the integer division mentioned in other answers.