java - 学校项目， double 取整。

我正在上课的贷款计算器。我快完成了，但是唯一缺少的是如何舍入INTEREST_RATE而不是$ 298.95833333333337，我希望获得$ 298.96。但是我不知道如何。

输入您的旧原则=
25000
输入您当前的付款=
450

上一个余额：$ 25000.0
付款：$ 450.0
已付利息：$ 151.04166666666666
支付的原理：$ 298.95833333333337
新校长：24701.041666666668

import java.util.Scanner;

public class LoanCalculator {

/**
 * @param args
 */
public static void main(String[] args) {
    // TODO Auto-generated method stub

    /**
     * Declaration Section
     *
     */
    Scanner keyboard = new Scanner(System.in);
    double INTEREST_RATE;
    double currentPayment;
    double oldPrincipal;
    double interestPaid;
    double principalPaid;
    double newPrincipal;


    /**
     * Process Section
     *
     */

    System.out.println("Enter your old Principle = ");
    oldPrincipal = keyboard.nextDouble();

    System.out.println("Enter your current payment = ");
    currentPayment = keyboard.nextDouble();

    INTEREST_RATE = 7.25 / 100.0; //fix this

    interestPaid = oldPrincipal * INTEREST_RATE / 12;

    principalPaid = currentPayment - interestPaid;

    newPrincipal = oldPrincipal - principalPaid;


    /**
     * Output Section
     *
     * */
    System.out.println("Previous Balance: " + "$"+ oldPrincipal);
    System.out.println("Payment: " + "$"+ currentPayment);
    System.out.println("Interest Paid: " + "$"+ interestPaid);
    System.out.println("Principle Paid: " + "$"+ principalPaid);
    System.out.println("New Principal: " + "$"+ newPrincipal);


}//Main()

}//LoanCalculator

最佳答案

编辑：我们应该使用BigDecimal类进行财务计算。
BigDecimal类具有内置的格式化程序，因此我添加了它。

编辑：
甚至按照@Basil Bourque的建议将舍入模式更改为一半。

      public class LoanCalculator {public static void main(String[] args) {
   Scanner keyboard = new Scanner(System.in);
    BigDecimal INTEREST_RATE, currentPayment, oldPrincipal, interestPaid, principalPaid, newPrincipal, month;
    System.out.println("Enter your old Principle = ");
    oldPrincipal = keyboard.nextBigDecimal();
    System.out.println("Enter your current payment = ");
    currentPayment = keyboard.nextBigDecimal();
    NumberFormat formatter = new DecimalFormat("#0.00");
    INTEREST_RATE = new BigDecimal(7.25 / 100.0);
    formatter.format(INTEREST_RATE);//only format
    month = new BigDecimal(12);
    interestPaid = INTEREST_RATE.multiply(oldPrincipal);
    interestPaid = interestPaid.divide(month, 2);
    principalPaid = currentPayment.subtract(interestPaid);
    newPrincipal = oldPrincipal.subtract(principalPaid);
    System.out.println("Previous Balance: " + "$" + oldPrincipal);
    System.out.println("Payment: " + "$" + currentPayment);
    System.out.println("Interest Paid: " + "$" + interestPaid.setScale(2, RoundingMode.HALF_EVEN)
            + " $" + formatter.format(interestPaid));
    System.out.println("Principle Paid: " + "$" + principalPaid.setScale(2, RoundingMode.HALF_EVEN)
            + " $" + formatter.format(principalPaid));
    System.out.println("New Principal: " + "$" + newPrincipal.setScale(2, RoundingMode.HALF_EVEN)
            + " $" + formatter.format(newPrincipal));}}