CODEWITHSUNDEEP
javacalculator
user14285182
user14285182

Reputation: 25

Java Compound interest calculator with annual contribution

I'm trying to make a program that calculates annual compound interest plus an additional annual contribution. My output correctly calculates the new balance when I make contributions = 0 but get the output wrong when I change the contribution.

    Scanner input1 = new Scanner(System.in);

    double amount;
    
    System.out.print("Enter starting year: ");
    Scanner input2 = new Scanner (System.in);
    
    System.out.print("Enter starting balance: ");
    Double principal = input1.nextDouble();

    System.out.print("Enter additional annual contribution: ");
    Double contribution = input1.nextDouble();

    System.out.print("Enter annual growth rate: ");
    Double rate = input1.nextDouble();
    Double rateDec = rate / 100

    for(int year = 1; year <= 21; year++){
        amount = (principal * Math.pow(1 + rateDec, year)) ;
        Double addedamount = amount + contribution;
        System.out.println(year + "  " + addedamount);

    }

my output is this

Principle = 10000
rate = 9.69

Contribution = 600

1  11569.0
2  12631.8961
3  13797.78683209
4  15076.65237611952
5  16479.439991365503
6  18018.157726528818
7  19705.977210229463
8  21557.346401900697
9  23588.113268244873
10  25815.6614439378
11  28259.05903785537
12  30939.221858623558
13  33879.09245672418
14  37103.83651578075
15  40641.05827415991
16  44521.036820926
17  48776.98528887373
18  53445.3351633656
19  58566.04814069572
20  64182.95820552914
21  70344.14685564491

but should be

1  11,569.00 
2  13,290.04 
3  15,177.84 
4  17,248.57 
5  19,519.96 
6  22,011.44 
7  24,744.35 
8  27,742.08 
9  31,030.29 
10 34,637.12 
11 38,593.46 
12 42,933.17 
13 47,693.39 
14 52,914.88 
15 58,642.33 
16 64,924.77 
17 71,815.99 
18 79,374.95 
19 87,666.39 
20 96,761.26

Upvotes: 0

Views: 519

Answers (1)

sgrpwr
sgrpwr

Reputation: 461

It looks like you want to calculate Compound Interest yearly with a contribution. I assume contribution is made every year at the start of the date starting from every first year.

As per my understanding:

public static void main(String[] args) {
    
    double contribution = 600; //Yearly contribution
    double initialAmount = 10000; 
    double rateOfInterest = 9.69; //9.96% per anum
    double years = 10;

    double rateFactor = 1 + rateOfInterest/100; //Rate factor = 1.969 if rate is 10%

    //Final calculation Assuming contribution is made on first day of year including first year also
    double finalAmount = initialAmount;
    for(int year=0; year<years; year++){
        System.out.println(year+" "+finalAmount+" "+contribution);
        
        finalAmount = finalAmount*rateFactor;
        finalAmount += contribution;
    }   
    
    System.out.println("Final Amount: "+finalAmount);
}

Its output will be:

0 10000.0 600.0
1 11569.0 600.0
2 13290.0361 600.0
3 15177.840598089999 600.0
4 17248.57335204492 600.0
5 19519.960109858075 600.0
6 22011.444244503324 600.0
7 24744.353191795697 600.0
8 27742.0810160807 600.0
9 31030.28866653892 600.0
10 34637.12363832654 600.0
11 38593.46091888038 600.0
12 42933.16728191989 600.0
13 47693.39119153792 600.0
14 52914.88079799795 600.0
15 58642.33274732395 600.0
16 64924.77479053964 600.0
17 71815.98546774292 600.0
18 79374.95445956722 600.0
19 87666.38754669928 600.0
Final Amount: 96761.26049997444

PS: For more clarity on the above calculation method, you should practice more on the Compound Interest section of Aptitude from any website.

Upvotes: 1

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