爪哇中方法逻辑的帮助

我有一个贷款类,在其printpayment方法中,它打印用于HW分配的贷款分期偿还表。我们还将实现打印第一付款方式和打印最后付款方式。由于我的计算是在printpayment方法中完成的,所以我不知道如何在循环的第一次或最后一次迭代中获取值并打印出该金额。

我能想到的一种方法是编写一个可能返回该值的新方法,但我不确定是否有更好的方法。这是我的代码:

public abstract class Loan
{   
    public void setClient(Person client)
    {
        this.client = client;
    }

    public Person getClient()
    {
        return client;
    }

    public void setLoanId()
    {
        loanId = nextId;
        nextId++;
    }

    public int getLoanId()
    {
        return loanId;
    }

    public void setInterestRate(double interestRate)
    {
        this.interestRate = interestRate;
    }

    public double getInterestRate()
    {
        return interestRate;
    }

    public void setLoanLength(int loanLength)
    {
        this.loanLength = loanLength;
    }

    public int getLoanLength()
    {
        return loanLength;
    }

    public void setLoanAmount(double loanAmount)
    {
        this.loanAmount = loanAmount;
    }

    public double getLoanAmount()
    {
        return loanAmount;
    }

    public void printPayments()
    {
        double monthlyInterest;
        double monthlyPrincipalPaid;
        double newPrincipal;
        int paymentNumber = 1;
        double monthlyInterestRate = interestRate / 1200;
        double monthlyPayment = loanAmount * (monthlyInterestRate) / 
                                (1 - Math.pow((1 + monthlyInterestRate),( -1 * loanLength)));

        System.out.println("Payment Number | Interest | Principal | Loan Balance");     

        // amortization table
        while (loanAmount >= 0) {
            monthlyInterest = loanAmount * monthlyInterestRate;
            monthlyPrincipalPaid = monthlyPayment - monthlyInterest;
            newPrincipal = loanAmount - monthlyPrincipalPaid;
            loanAmount = newPrincipal;


            System.out.printf("%d, %.2f, %.2f, %.2f", paymentNumber++, monthlyInterest, monthlyPrincipalPaid, loanAmount);
        }
    }
    /*
    //method to print first payment
    public double getFirstPayment()
    {
    }

    method to print last payment
    public double getLastPayment()
    {
    }*/

    private Person client;
    private int loanId;
    private double interestRate;
    private int loanLength;
    private double loanAmount;
    private static int nextId = 1;

}

谢谢!