java - 摄氏度到华氏度转换器程序中的语法错误

Question

我必须允许用户选择要进行的转换以及从什么程度开始，然后打印从该程度开始直到接下来的 9 个转换(10 个转换)的转换。我必须使用回调函数来编写它。开头还有一个菜单。我在 line 处有一个“else without if”。另外，我的回调函数无法正确计算数字。如何解决此错误并修复我的回调函数？

import java.util.Scanner;

public class FahrToCel {

    public static Scanner input = new Scanner(System.in);

    public static void main(String[] args) {

        double choice = 0;
        double fahrenheit = 0;
        double celsius = 0;
        double answer = 0;


        //print the welcome message and the menu options for the user
        System.out.printf("Welcome to Candace's Fahrenheit and Celsius "
            + "convertor. ");
        System.out.printf("Please choose one of the following options: \n"
            + " Press 0 to exit \n Press 1 to to convert to Celsius \n"
            + " Press 2 to convert to Fahrenheit >  ");
        choice = input.nextInt();

        //print what happens when the user hits a button
        if (choice == 0){ 
            // the user is going to exit the game
            System.out.printf("Well hopefully you can play again soon! :) ");
        } else {
            //perform code for the operation
            for ( double i = fahrenheit; i >-100; i-=10 ){
                if (choice == 1) { 
                    // it will convert from fahrenheit to celsius
                    System.out.printf("Please pick a number in Fahrenheit: > ");
                    fahrenheit = input.nextDouble();
                    celsius = FahrToCel();
                    System.out.printf("%f ", i);
                }
            }
            for ( double i = celsius; i >-10; i-=10 ){
                if (choice == 2){ 
                    // it will convert from celsius to fahrenheit
                    System.out.printf("Please pick a number in celsius: > ");
                    celsius = input.nextDouble();
                    fahrenheit = CelToFahr();
                    System.out.printf("%f ", i);
                }
            } 

        } else {
            System.out.printf("I'm sorry, I did not ask you to enter that "
                + "number. ");
        }
    }

    public static double CelToFahr(){
        double celsius = 0;
        double fahrenheit = 0;
        celsius = (fahrenheit - 32) * (5.0/9.0);
        return celsius;
    }

    public static double FahrToCel( ){
        //perform the conversion for fahrenheit to celsius
        double celsius = 0;
        double fahrenheit = 0;
        fahrenheit = ((9.0/5.0) + 32) * celsius;
        return fahrenheit;

    }

}

Answer 1

您正在寻找这样的结构

if (choice == 0){
    // ...
}
else if (choice == 1) {
    for ( double i = fahrenheit; i >-100; i-=10 ){
        // ...
    }
}
else if (choice == 2) {
    for ( double i = celsius; i >-10; i-=10 ){
        // ...
    }
}
else {
    // ...
}

现在，您在 else 内有一些 if 语句，并且您的范围变得困惑。然后，您的循环将进入那些 else if 语句内部。另请注意，您进行了多次转换，但打印每次输入的初始值，而不是转换后的温度。