如何计算一大堆不同的扫描仪输入

Question

我不确定如何为此进行计算。 我把一切都做好了，直到我试图真正获得投资金额。 我知道我现在拥有的是错误的，但谷歌对我并没有超级帮助，我的书只是没有我需要的东西来完成这个的事情。

这是我现在所拥有的

import java.util.Scanner;
class InvestmentCalculator {
    public static void main(String[] args) {
        // create a scanner object
        Scanner input = new Scanner(System.in);
        // Prompt user to enter investment amount
        Scanner amount = new Scanner(System.in);
        System.out.println("Enter Investment Amount");
        while (!amount.hasNextDouble()) {
            System.out.println("Only Integers");
            amount.next();
        }
        //Promt user to enter interest rate
        Scanner interest = new Scanner(System.in);
        System.out.println("Enter Interest Percentage in decimals");
        while (!interest.hasNextDouble()) {
            System.out.println("Just like before, just numbers");
            interest.next();
        }
        //Prompt user to enter number of years
        Scanner years = new Scanner(System.in);
        System.out.println("Enter Number of Years");
        while (!years.hasNextDouble()) {
            System.out.println("Now you are just being silly. Only Numbers allowed");
            years.next();
        }
        //Compute Investment Amount
        double future = amount * Math.pow((1 + interest), (years * 12));
        //Display Results
        System.out.println("Your future investment amount is " + future);
    }
}

任何帮助都会非常非常有帮助！

Answer 1

首先amount，interest和years是Scanners，它们不是数字。 Scanner可能包含任意数量的不同类型的内容，因此像Math.pow这样的东西不可能知道它应该如何处理它们。

您需要将从用户那里读取的值分配给某些变量。

我会从使用单个Scanner开始，比如说叫kb...

Scanner kb = new Scanner(System.in);

然后在您想从用户那里获取值时使用它......

你的输入循环对我来说似乎是错误的，我对Scanner不是特别有经验，所以可能有更好的方法来实现这一目标，但是......

int invest = -1; // amount
double rate = -1; // percentage
int period = -1; // period
do {
    System.out.println("Only Integers");
    String text = kb.nextLine();
    try {
        invest = Integer.parseInt(text);
    } catch (NumberFormatException exp) {
        System.out.println("!! " + text + " is not an integer");
    }
} while (invest == -1);
System.out.println(invest);

一旦你有了你需要的所有信息，就用这些基元类型进行计算......

double future = invest * Math.pow((1 + rate), (period * 12));

<</div> div class="one_answers">

您不必为此使用 4 个不同的扫描仪，因为您正在从同一个流中读取......你的代码应该是这样的——

import java.util.Scanner;

类投资计算器 {

public static void main(String[] args) {
     double amount=0;
     int interest=0;
     double years=0;
    // create a scanner object
    Scanner input = new Scanner(System.in);
    // Prompt user to enter investment amount
    Scanner amount = new Scanner(System.in);
    System.out.println("Enter Investment Amount");
    while (!input.hasNextDouble()) {      // you say you only want integers and are           
                                          // reading double values??
        System.out.println("Only Integers");
        amount = input.nextDouble();   
    }
    //Promt user to enter interest rate
    System.out.println("Enter Interest Percentage in decimals");
    while (!input.hasNextInt()) {
        System.out.println("Just like before, just numbers");
      interest= input.nextInt();
    }
    //Prompt user to enter number of years
    System.out.println("Enter Number of Years");
    while (!input.hasNextDouble()) {
        System.out.println("Now you are just being silly. Only Numbers allowed");
      years=input.nextDouble();
    }
    //Compute Investment Amount
    double future = amount * Math.pow((1 + interest), (years * 12));
    //Display Results
    System.out.println("Your future investment amount is " + future);
}

}