Question

嘿我这个代码一直有问题，因为当我输入String重复的值时它还没有循环。我无法理解我做错了什么。

import java.util.Scanner;
public class MpgCalculator
{
    public static void main(String[]args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Welcome to the MPG and CPM Calculator!");
        double startOd, endOd, gallons, cost, mpg, cpm;
        String repeat = "yes";
        while(repeat.equals("yes")||repeat.equals("Yes")||repeat.equals("y")||repeat.equals("Y"))
        {
            System.out.println("Please Enter:");
            System.out.print("\tYour Starting Odometer Reading: ");
            startOd = sc.nextDouble();
            System.out.print("\tYour Ending Odometer Reading: ");
            endOd = sc.nextDouble();
            System.out.print("\tThe Amount of Gallons Used: ");
            gallons = sc.nextDouble();
            System.out.print("\tThe Cost-per-Gallon That You Spent: ");
            cost = sc.nextDouble();
            mpg = getMpg(startOd, endOd, gallons);
            cpm = getCpm(mpg, cost);
            System.out.println("\nYour Miles-per-Gallon is " + mpg + ".");
            System.out.println("Your Cost-per-Mile is " + cpm + ".");
            System.out.print("Do it again? ");
            repeat = sc.nextLine();
        }
    }
    public static double getMpg(double startOd, double endOd, double gallons)
    {
        double mpg;
        mpg = (endOd - startOd) / gallons;
        return mpg;
    }
    public static double getCpm(double mpg, double cost)
    {
        double cpm;
        cpm = cost / mpg;
        return cpm;
    }
}

Answer 1

将repeat = sc.nextLine();更改为repeat = sc.next();如果您不需要额外的行。只有当你是下一行时才会得到它，你不是这样，所以它终止了程序。

Answer 2

在Scanner循环中调用repeat = sc.nextLine();之前，while之前的使用是nextDouble。调用nextDouble不会消耗流中的换行符来输入每加仑的成本。

在要求重复之前使用换行符：

System.out.print("Do it again? ");
String dummy = sc.nextLine();  // Add this line.
repeat = sc.nextLine();

Answer 3

使用 repeat = sc.next（）; 代替 repeat = sc.nextLine（）;

虽然语句循环错误

3 个答案: