Java - 需要帮助使我的计算程序更高效，使用数组？

Question

我目前正在学习 Java 语言，这是我的第一门编程语言。我对数组进行了研究，并试图让我的程序更高效、更简单。我意识到原始代码中有很多重复。我感谢任何提示和批评。

import java.util.Scanner;

public class Calculator {

static Scanner sc = new Scanner(System.in);//sets up scanner import

public static void main(String[] args) 
{
    double initalInvestment;
    double interestRate;
    int yearsInvested;
    int arrInt[] = new int[5];

    arrInt[0] = 1;

    int i = 1;
    while (i <= 4) {
        arrInt[i] = i + 1;
        i++;
    }

    System.out.println("Enter Inital Investment: ");
    initalInvestment = sc.nextDouble();

    System.out.println("Enter Interest Rate: ");
    interestRate = sc.nextDouble();

    System.out.println("Enter Years Invested: ");
    yearsInvested = sc.nextInt();

    double money1 = initalInvestment * interestRate;

    double money2 = money1 + initalInvestment;

    double y1 = money2;
    double y2 = y1 * interestRate + y1;
    double y3 = y2 * interestRate + y2;

    if (yearsInvested <= 1) 
    {
    System.out.println("Your Total for year: " + arrInt[0] + ", is " + y1 + "$");
    } else if (yearsInvested <= 2) {
        System.out.println("Your Total for year: " + arrInt[0] + ", is " + y1 + "$");
        System.out.println("Your Total for year: " + arrInt[1] + ", is " + y2 + "$");
    } else if (yearsInvested <= 3) {
        System.out.println("Your Total for year: " + arrInt[0] + ", is " + y1 + "$");
        System.out.println("Your Total for year: " + arrInt[1] + ", is " + y2 + "$");
        System.out.println("Your Total for year: " + arrInt[2] + ", is " + y3 + "$");
    } else if (yearsInvested <= 4) {
        System.out.println("Your Total for year: " + arrInt[0] + ", is " + y1 + "$");
        System.out.println("Your Total for year: " + arrInt[1] + ", is " + y2 + "$");
        System.out.println("Your Total for year: " + arrInt[2] + ", is " + y3 + "$");
        System.out.println("Your Total for year: " + arrInt[3] + ", is " + y3 + "$");
    } else if (yearsInvested <= 5) {
        System.out.println("Your Total for year: " + arrInt[0] + ", is " + y1 + "$");
        System.out.println("Your Total for year: " + arrInt[1] + ", is " + y2 + "$");
        System.out.println("Your Total for year: " + arrInt[2] + ", is " + y3 + "$");
        System.out.println("Your Total for year: " + arrInt[3] + ", is " + y3 + "$");
    }

 }

}

Answer 1

您不希望yearsInvested 的每个可能值都有明确的案例。这种方法意味着您可能正在复制粘贴代码并稍作修改，这很容易出错 - 事实上，我看到了复制粘贴错误；您的 5 年案例只有 4 年，y3 在 4 年和 5 年案例中被列出两次。 （想象一下，如果乔治华盛顿自 1776 年以来不理会它，他花了 241 年的时间来计算目前在他的银行账户中的金额——这将是一个不合理的代码量。）

现在，您的数组的内容只是 {1,2,3,4,5}。你当然不需要一个数组来数到五。我不相信这个程序需要一个数组（你可能只是在一个 for 循环中同时完成输入和输出），但如果你想使用一个，把你的结果放在里面的计算。

您可以使用for 循环将内容放入数组并从数组中读取值 - 例如，从数组中读取值可能如下所示：

for (int i = 0; i < yearsInvested; x++)
{
    System.out.println("Your Total for year: " + (i+1) + ", is " + resultsArray[i] + "$");
}

Answer 2

您根本不需要存储总数 - 如果您所做的只是打印出每年的累计总数，那么您可以随时计算：

double investment = scanner.nextDouble();
...

for (int year = 0; year < yearsInvested; year++) {
    investment += investment * interestRate;
    System.out.println("Total year " + year + " is " + investment);
}

如果您确实需要存储这些值，那么我建议您使用 List 而不是数组。对于初学者来说，它们更容易学习。

List<Integer> totals = new ArrayList<>();
for (int year = 0; year < yearsInvested; year++) {
    investment += investment * interestRate;
    totals.add(investment);
}