Java Programming

I am developing an Application to essentially figure out the interest and principal on a loan a selected number of payments. I have read that it is best to use BigDecimal to ensure accurate caluations, but I am not getting correct results and wondering if someone would help me.






The algorithm to calculate period principal and period interest is :

peridocicInterest amount = Remainging Balance * periodic interest rate
periodicPrincipal amount = payment - peridocicInterest amount
Remainging Balance = Remainging Balance - periodicPrincipal amount

public class Loan {

    private double payment;
    private double interestRate;
    private int amoritizationTerm;
    private int actualTerm;
    private double loanAmount;
    private double downPayment;
    private double remaingingBalance;


    public Loan(double interestRate, int amoritizationYears, int actualTerm, double loanAmount, double downPayment) {
        
        
        
        amoritizationTerm = amoritizationYears * 12;
        this.interestRate = (interestRate/100.00)/12;
        this.actualTerm = actualTerm;
        this.loanAmount = loanAmount;
        this.downPayment = downPayment;

        remaingingBalance = this.loanAmount - this.downPayment;

        public double calculatePayment()
    {


        
           double tmpPayment = Math.abs(FinanceLib.pmt(interestRate, amoritizationTerm, loanAmount, 0, false));
           BigDecimal bdPayment = new  BigDecimal(tmpPayment);
           
           bdPayment = bdPayment.setScale(2, RoundingMode.HALF_EVEN);
           System.out.println(bdPayment);


           return payment = bdPayment.doubleValue();
    }


        public double amoritzeLoan()
    {

       BigDecimal bdPayment;
       BigDecimal bdRemainingBalance = new BigDecimal(remaingingBalance);

        if(payment <= remaingingBalance)
        {
            bdPayment = new  BigDecimal(payment);
        }
        else
        {
            bdPayment = new  BigDecimal(remaingingBalance);
        }

       bdPayment = bdPayment.setScale(2, RoundingMode.HALF_EVEN);


       //Periodic Interest Rate
        BigDecimal bdInterest = new  BigDecimal(interestRate);
        bdInterest = bdInterest.setScale(13, RoundingMode.HALF_EVEN);



        //Calculate Amount of Interest Charged in Period
        BigDecimal bdPeriodInterest = new BigDecimal(0);
        bdPeriodInterest = bdRemainingBalance.multiply(bdInterest);
        bdPeriodInterest = bdPeriodInterest.setScale(2, RoundingMode.HALF_EVEN);
        
        //Calculate Principal gained in Period
        BigDecimal bdPeriodPrincipal = new BigDecimal(0);
        bdPeriodPrincipal =  bdPayment.subtract(bdPeriodInterest).setScale(2, RoundingMode.HALF_EVEN);

        System.out.println("Period Interest " + bdPeriodInterest);
        System.out.println("Period Interest " + bdPeriodPrincipal);


        

        //Create Amoritization Table
        for(int i = 0; i < amoritizationTerm; i++)
        {



            //Check that Remainging Balance isn't < Payment
            if(bdPayment.doubleValue() > bdRemainingBalance.doubleValue())
            {
                bdPayment = bdRemainingBalance;
            }

            
            //Calculate Amount of Interest Charged in Period
            bdPeriodInterest = new BigDecimal(0);
            bdPeriodInterest = bdRemainingBalance.multiply(bdInterest);
            bdPeriodInterest = bdPeriodInterest.setScale(2, RoundingMode.HALF_EVEN);

            
            //Calculate Principal gained in Period
            bdPeriodPrincipal = new BigDecimal(0);
            bdPeriodPrincipal =  bdPayment.subtract(bdPeriodInterest).setScale(2, RoundingMode.HALF_EVEN);

            bdRemainingBalance = bdRemainingBalance.subtract(bdPeriodPrincipal);


            System.out.println("Principal = " + bdPeriodPrincipal + " Interest = " + bdPeriodInterest + " Balance = " + bdRemainingBalance);
                      //System.out.println("Principal = " + bdPeriodPrincipal + " Interest = " + bdPeriodInterest );

        }



        
        //Interest
        return bdPayment.subtract(bdPeriodInterest).setScale(2, RoundingMode.HALF_EVEN).doubleValue();
    }

    }

Output from the for the first 3 payments is for loan amount 50000 at 6 % interest for 30 years

Principal = 49.78 Interest = 250.00 Balance = 49950.22
Principal = 50.03 Interest = 249.75 Balance = 49900.19
Principal = 50.28 Interest = 249.50 Balance = 49849.91

*The principal and interest and Balance amount are wrong starting with the 2nd payment.  Does anyone have any idea what I did wrong?*