Java行程燃油成本计算程序运行报错排查求助

错误原因 #

• 最核心的问题是Java语法强制要求所有方法必须定义在类的内部，你当前的代码直接在全局范围编写了calcFuelNeeded、calcGallonsFuelNeeded、calcCostNeeded三个静态方法以及main方法，没有外层的类包裹，不符合Java语法规范，因此编译报错。
• 你代码里用到的Math.ceil属于java.lang包下的工具类，默认会自动导入，不需要额外添加import语句。

修正后的完整代码 #

import java.util.Scanner;

// 新增外层类包裹所有方法，类名可以和文件名保持一致
public class FuelCostCalculator {
  /**   
    * Calculates the amount of fuel needed.
    *
    * @param distance The distance of the trip.
    * @param milesPerLiter Total distance that could be achieved with 1 liter of fuel.
    * @return Total fuel needed.
    */
    public static double calcFuelNeeded(double distance, double milesPerLiter) {
               double fuelNeeded = distance / milesPerLiter;
               return fuelNeeded;
    }

   /**   
    * Calculates the total number of gallons needed.
    *
    * @param fuelNeeded Total fuel needed.
    * @param litersPerGallon The volume of each gallon.
    * @return Total number of gallons needed.
    */
    public static int calcGallonsFuelNeeded(double fuelNeeded, double litersPerGallon) {
                double gallonsFuel = Math.ceil(fuelNeeded / litersPerGallon);
                return (int) gallonsFuel;
    }

   /**   
    * Calculates the total cost needed.
    *
    * @param gallonsFuel Total number of gallons needed.
    * @param costPerGallon The cost of each gallon.
    * @return The total cost of the trip.
    */
    public static double calcCostNeeded(int gallonsFuel, double costPerGallon) {
               double costNeeded = gallonsFuel * costPerGallon;
               return costNeeded;
    }

    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        System.out.println("Enter the distance to be covered (miles):");
        double distance = scnr.nextDouble();
        double milesPerLiter = 13.7;
        double litersPerGallon = 3.785;
        double costPerGallon = 2.629;
        
        scnr.close();
        
        System.out.println("Fuel Needed: " + calcFuelNeeded(distance, milesPerLiter) +  " liter(s)");
        System.out.println("Gallons needed: " + calcGallonsFuelNeeded( calcFuelNeeded(distance, milesPerLiter),  litersPerGallon) + " gallon(s)");
        System.out.println("Cost needed: " +calcCostNeeded( calcGallonsFuelNeeded( calcFuelNeeded(distance, milesPerLiter),  litersPerGallon),  costPerGallon) + " $");
    }
}

内容的提问来源于stack exchange，提问作者ZJR