用户输入问题的代码双方程错误

Question

我的第一个任务是开发一个代码，允许用户输入他们希望行驶的距离（以英里为单位）、燃油效率和汽油成本的数据。然后创建一个代码以计算旅行的总费用。

我有所有输入值的所有代码，但我在处理方程式本身时遇到了问题。 Java 无法识别“/”。我无法理解我在做什么，除非我需要为方程式添加更多代码。

import java.util.Scanner;
public class DrivingCost
{
    public static void main(String args[])
    {
        Scanner s = new Scanner(System.in);
        System.out.print("Please enter your distance (miles): ");

      Scanner t = new Scanner(System.in);
      System.out.print("Please enter vehicle's fuel efficiency (mpg): ");

      Scanner u = new Scanner(System.in);
      System.out.print("Please enter the price per gallon (dollars): ");

      String distanceInMiles = s.nextLine();
      System.out.println("The distance (miles): " + distanceInMiles);

      String fuelEfficiency = t.nextLine();
      System.out.println("Fuel efficiency (mpg):" + fuelEfficiency);

        String pricePerGallon = u.nextLine();
        System.out.println("Price per gallon (dollars): " + pricePerGallon);

      double tripCost = (distanceInMiles / fuelEfficiency) * pricePerGallon;
      System.out.println("The trip cost (dollars): " + tripCost);
    }
}

这是我一直收到的错误：

DrivingCost.java:32: error: bad operand types for binary operator '/'
  double tripCost = (distanceInMiles / fuelEfficiency) * pricePerGallon;
                                     ^

Answer 1

您可以使用 s.nextDouble() 在 double 中获得 distanceInMiles、fuelEfficiency 和 pricePerGallon。之后，您应该能够对这些变量执行 double 操作。

public static void main(String args[])
  {
    Scanner s = new Scanner(System.in);

    System.out.print("Please enter your distance (miles): ");
    double distanceInMiles = s.nextDouble();
    System.out.println("The distance (miles): " + distanceInMiles);

    System.out.print("Please enter vehicle's fuel efficiency (mpg): ");
    double fuelEfficiency = s.nextDouble();
    System.out.println("Fuel efficiency (mpg):" + fuelEfficiency);

    System.out.print("Please enter the price per gallon (dollars): ");
    double pricePerGallon = s.nextDouble();
    System.out.println("Price per gallon (dollars): " + pricePerGallon);

    double tripCost = (distanceInMiles / fuelEfficiency) * pricePerGallon;

    System.out.println("The trip cost (dollars): " + tripCost);
  }

Answer 2

您正在尝试使用字符串进行计算。您必须从字符串输入中解析双精度数。只需将方程行更改为：

double tripCost = (Double.valueOf(distanceInMiles) / Double.valueOf(fuelEfficiency)) * Double.valueOf(pricePerGallon);

P.S。适当的输入验证将是一个很好的改进。以防用户提供不正确的输入。此外，如评论中所述，无需使用多个 Scanners。一个就够了

Answer 3

你正在对字符串进行数学运算，你不能，你需要 double 类型
- Double.parseDouble(sc.nextLine()); 读取一行并解析为 double（好处：通常避免 return 行错误，养成好习惯）
- sc.nextDouble() 直接读取 double
每个来源仅使用一个扫描器
在print和扫描仪询问

Scanner sc = new Scanner(System.in);

System.out.print("Please enter your distance (miles): ");
String distanceInMiles = Double.parseDouble(sc.nextLine());
System.out.println("The distance (miles): " + distanceInMiles);

System.out.print("Please enter vehicle's fuel efficiency (mpg): ");
String fuelEfficiency = Double.parseDouble(sc.nextLine());
System.out.println("Fuel efficiency (mpg):" + fuelEfficiency);

System.out.print("Please enter the price per gallon (dollars): ");
String pricePerGallon = Double.parseDouble(sc.nextLine());
System.out.println("Price per gallon (dollars): " + pricePerGallon);

double tripCost = (distanceInMiles / fuelEfficiency) * pricePerGallon;
System.out.println("The trip cost (dollars): " + tripCost);

用户输入问题的代码双方程错误

Code Double Equation Error for User Input Problem

java

math

equation

input