用於計算興趣的Java程序

Question

因此，我正在進行一項學校任務（痛苦地），並且我已經整理了這個特定的問題，減去了一些細節。該計劃基本上爲15個人計算隨機月度儲蓄，介於100美元和800美元之間，然後打印每月保存的金額，該月賺取的利息以及一年的總收入。這是代碼。我不會打擾張貼我的EmployeeSavings類擴展了通訊錄類，因爲它不是真正的問題相關....

import java.util.Arrays; 

public class EmployeeSavings extends AddressBook { 

private double accountValue; 
private double[] monthlyInterests; 
private double[] monthlySavings; 
public static final double ANNUAL_INTEREST_RATE = 0.05; 

public EmployeeSavings(String firstName, String lastName) { 
    super(firstName, "", lastName); 
} 

public EmployeeSavings(String firstName, String lastName, double[] d1, double[] d2) { 
    super(firstName, "", lastName); 
    this.monthlySavings = d1; // .length? 
    this.monthlyInterests = d2; // .length? 
} 

public double getAccountValue() { 
    return accountValue; 
} 

public double[] getMonthlyInterests() { 
    return monthlyInterests; 
} 

public double[] getMonthlySavings() { 
    return monthlySavings; 
} 

public double[] calculateInterests() { 
    accountValue = 0; 
    for (int n = 0; n < monthlyInterests.length; n++) { 
     accountValue += monthlySavings[n]; 
     monthlyInterests[n] = (accountValue * (ANNUAL_INTEREST_RATE/12)); 
     accountValue += monthlyInterests[n]; 
    } 
    accountValue = accountValue; 
    return monthlyInterests; 
} 

public double[] generateMonthlySavings() { 
    for (int n = 0; n < monthlySavings.length; n++) { 
     monthlySavings[n] = (Math.random() * 700 + 100); 
    } 
    return monthlySavings; 
} 

public static String getReport(EmployeeSavings[] arr) { 
    String report = ""; 
    for (EmployeeSavings calculate : arr) { 
     calculate.calculateInterests(); 
     report += "<" + calculate.getFirstName() + " " + calculate.getLastName() 
     + "> \n\nMonthly savings for 12 months: \n" 
     + Arrays.toString(calculate.getMonthlySavings()) 
     + "\n\nInterest earned for each month: \n" 
     + Arrays.toString(calculate.getMonthlyInterests()) 
     + "\n\nTotal account value after 12 months: $" + calculate.getAccountValue() + "\n\n\n"; 
    } 
    return report; 
} 


} 

，並且測試類....

public class TestEmployeeSavings { 

public static void main(String[] args) { 

    EmployeeSavings[] employees = new EmployeeSavings[] { 
      new EmployeeSavings("Elena", "Brandon", new double[12], new double[12]), 
      new EmployeeSavings("Thomas", "Molson", new double[12], new double[12]), 
      new EmployeeSavings("Hamilton", "Winn", new double[12], new double[12]), 
      new EmployeeSavings("Suzie", "Sarandin", new double[12], new double[12]), 
      new EmployeeSavings("Philip", "Winne", new double[12], new double[12]), 
      new EmployeeSavings("Alex", "Trebok", new double[12], new double[12]), 
      new EmployeeSavings("Emma", "Pivoto", new double[12], new double[12]), 
      new EmployeeSavings("John", "Lenthen", new double[12], new double[12]), 
      new EmployeeSavings("James", "Lean", new double[12], new double[12]), 
      new EmployeeSavings("Jane", "Ostin", new double[12], new double[12]), 
      new EmployeeSavings("Emily", "Car", new double[12], new double[12]), 
      new EmployeeSavings("Daniel", "Hamshire", new double[12], new double[12]), 
      new EmployeeSavings("Neda", "Bazdar", new double[12], new double[12]), 
      new EmployeeSavings("Aaron", "Smith", new double[12], new double[12]), 
      new EmployeeSavings("Kate", "Hen", new double[12], new double[12]) }; 

    for (EmployeeSavings calculate : employees) { 
     calculate.generateMonthlySavings(); 
    } 
    System.out.println(EmployeeSavings.getReport(employees)); 





} 
} 

的輸出我得到每個人是這樣的：

每月可節省12個月： [419.33855414289945，685.3556014985876，750.0193923605882，419.55644434159916，689.0894339019552，114.41141555507095，266.1838438533235，136.00655226158167，232.40836179739927 ，577.1312357147676，535.620933915401，451.8150715112862]

所得利息爲每個月： [1.7472439755954143，4.61017249840451，7.754462351983647，9.53492446320691，12.445859289728418，12.974431268248416，14.137590747921632，14.763191343794562，15.793072815216203，18.26359076742447，20.57144295360291，22.539720097206615]

總帳戶價值：$ 5432.072543426794

我想知道如何調整我的儲蓄/利息方法，以便每個金額都打印到小數點後第二位（適當的美元金額），之前有一個$符號。我還注意到，每個儲蓄金額/利息的列表都包含在[]中，這有點令人討厭，我想解決這個問題，但不知道如何解決。任何幫助將不勝感激！ :)

P.S. EmployeeSavings類中的所有變量/方法都需要作爲該程序的預期API的一部分，並且他們似乎不願意偏離它們，所以這不是一個真正的選擇。

Answer 1

NumberFormat n = NumberFormat.getCurrencyInstance(Locale.US); 
double value = your Number; 
String s = n.format(doublePayment); 

這是你在找什麼？