java - 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(英里)、燃油效率和汽油成本的数据。然后创建一个代码以计算行程的总费用。

我拥有所有输入值的所有代码，但我在方程本身方面遇到了麻烦。 Java 无法识别“/”。我无法理解我在做什么，除非我需要添加更多代码才能使方程发挥作用。

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);
    }
} 

这是我不断收到的错误:

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

Answer 1

1. 您正在对字符串进行数学运算，但不能，您需要 double 类型
   • Double.parseDouble(sc.nextLine()); 读取一行并解析为 double (好处:避免一般情况下返回行错误，这是一个好习惯)
   • sc.nextDouble() 直接读取 double
2. 每个来源仅使用一台扫描仪
3. 在打印和扫描仪询问之间保持良好的顺序

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);