Java未正确使用Scanner类[重复]

Question

我是一个程序员新手，这似乎是一个很简单的问题，但我相当卡住，甚至在周围看了2个小时左右。我的代码贴在下面，唯一的问题是扫描器类没有要求输入。（决定用加仑对升还是用升对加仑）如果有人帮我解决这个问题，我会非常感激的

import java.util.Scanner;
public class GallonsToLiters {

public static void main(String[] args) {
    System.out.println("Do you want liters or gallons? Enter a 10 for gallons to liters, and anything else for liters to gallons.");

    Scanner test = new Scanner(System.in);


    if (test.equals (10)){
        double gallons, liters;
            Scanner console = new Scanner(System.in);

            System.out.println("Enter an amount of gallons --> ");
            gallons = console.nextDouble();
            liters = gallons * 3.785;
            // "%.2f" means that it rounds to 2 dec places. If you change #, that is how many decimal places it rounds to
            System.out.printf("Amount in liters " + "%.2f",liters);
    }
     else{
            double liters01, gallons01;
            Scanner console01 = new Scanner(System.in);

            System.out.println("Enter an amount of liters --> ");
           liters01 = console01.nextDouble();
            gallons01 = liters01 / 3.785;
            // "%.2f" means that it rounds to 2 dec places. If you change #, that is how many decimal places it rounds to
            System.out.printf("Amount in gallons (Rounded) " + "%.2f",gallons01);




            }

Answer 1

不需要声明扫描多个对象一次，不需要为每个条件结构声明不同的加仑和升变量

Scanner reader = new Scanner(System.in);
double gallons, liters;
int op;
System.out.println("Do you want liters or gallons? Enter a 10 for gallons to liters, and anything else for liters to gallons.");

 op = reader.nextInt();

if (op==10){

        System.out.println("Enter an amount of gallons --> ");
        gallons = reader.nextDouble();
        liters = gallons * 3.785;
        // "%.2f" means that it rounds to 2 dec places. If you change #, that is how many decimal places it rounds to
        System.out.printf("Amount in liters " + "%.2f",liters);
}
 else{


        System.out.println("Enter an amount of liters --> ");
        liters = reader.nextDouble();
        gallons = liters/3.785;
        // "%.2f" means that it rounds to 2 dec places. If you change #, that is how many decimal places it rounds to
        System.out.printf("Amount in gallons (Rounded) " + "%.2f",gallons);
        }
}