Question

所以基本上，我的程序编译正确并且正在工作。但是，当程序计算简单兴趣时，它会显示不正确的值。假设它应该显示470美元，而不是只打印出4.7，对不起的解释感到抱歉，有人能弄明白为什么会发生这种情况吗？

import java.io.*;
import java.util.Scanner;
import java.io.File;
//import java.nio.file.*;
//import java.nio.file.Paths;
public class BankInterest {

  public static void main (String [] args) throws IOException
  {

    /* TASK 1: Declare variables */

  Scanner user_input = new Scanner (System.in);

  boolean exit;
  int accountType;
    double balance;
    double principal;
  // double userInterest;
  double r;
  double r2;
  int year;

  String commBank = ("commbank.txt");
  String westPac = ("westpac.txt");

    /*Check if the expected command line is provided */

  if (args.length < 1) {
    /* Display the Usage */
    System.out.println("Usage: java BankInterest interestRateFileName");
    /* Programs quits with an error code */
    System.exit(-1);
 }

    /* TASK 2: Read interest rates from a file */

    String filename = (args[0]);
    Scanner textReader = new Scanner(new File(filename));
    r = textReader.nextDouble();
    r2 = textReader.nextDouble();
    System.out.println(r);
    System.out.println(r2);

    /* TASK 3: Take user input - Which Account */

    Scanner keyboard = new Scanner (System.in);
    System.out.println("Which Account: ");
    System.out.println("1 - Savings");
    System.out.println("2 - Term Deposits");

    accountType = keyboard.nextInt();

    if (accountType == 1) {
      accountType = 1;
 }
    else if (accountType == 2) {
      accountType = 2;
 }

    /* TASK 4: Take user input - Principal and Period */

    Scanner input = new Scanner (System.in);
    System.out.println("Principal: ");
    principal = keyboard.nextDouble();

    System.out.println("Years: ");
    year = keyboard.nextInt();

    /* TASK 5: Calculate balance for the chosen account type */

    if (accountType == 1) {
      double userBalance = principal * Math.pow((1 + r/100), year);
        double userInterest = userBalance-principal;
        System.out.println("");
      System.out.println("The Compound Interest is: " + userBalance);
    System.out.println("The total amount of Interest earned:" + userInterest);
  }
    else if (accountType == 2) {
      double userBalance = (principal * r2 * year) / 100;
        double userInterest = userBalance-principal;
     System.out.println("");
      System.out.println("The Simple Interest is: " + userBalance);
    System.out.println("The total amount of Interest earned:" + userInterest);

  }
 }
}

Answer 1

首先，公式是错误的。正确的是（假设r2代表％）：

double userInterest = (principal * r2 * year) / 100;
double userBalance = principal + userInterest;

Answer 2

我想这只是因为你给出了利率百分比。我的意思是20％的利率，你的文件中的值是0.20。在你的计算中，你再将它除以100。在您的计算中，将您的兴趣值更改为20或将除法除以100。

编程新手，需要一些帮助

2 个答案: