当用户在循环内的任何输入中输入 -1 时如何停止 Java 程序？

Question

我有一个代码，要求用户一个接一个地输入多个值，这对 N 个用户重复，直到 (-1) 输入 any 循环内的值。下面是我的代码，没有循环，因为我不确定如何去做，它也没有计数器来找出 N 是什么（我稍后会添加）。

public class Test{
    public static void main(String[] args){
        int id;
        int tempId;
        int age;
        int tempAge;
        int carbs;
        int fat;
        int protein;
        int totalGrams;
        int totalCalories;
        int sumGrams = 0;
        int sumCalories = 0;
        
        double percentCarbs;
        double percentFat;
        double percentProtein;
        double ratio = 0;
        double tempRatio;
        
        Scanner in = new Scanner (System.in);
        System.out.print("Please enter your ID:");
        tempId = in.nextInt();
        
        
        System.out.print("Please enter your age:");
        tempAge = in.nextInt();
        
        System.out.print("Please enter the amount of carbohydrates consumed (in grams):");
        carbs = in.nextInt();
        
        System.out.print("Please enter the amount of fat consumed (in grams):");
        fat = in.nextInt();
        
        System.out.print("Please enter the amount of protein consumed (in grams):");
        protein = in.nextInt();
        
        totalGrams = TotalGrams(carbs, fat, protein);
        totalCalories = TotalCalories(carbs, fat, protein);
        
        sumGrams += totalGrams;
        sumCalories += totalCalories;
        
        percentCarbs = Percentage(carbs*4, totalCalories);
        percentFat = Percentage(fat*9, totalCalories);
        percentProtein = Percentage(protein*4, totalCalories);
        
        tempRatio = ProteinEnergyRatio(carbs, fat, protein);
        
        System.out.println("\nThe total number of Grams consumed is "+totalGrams +" and the total number of Calories consumed is "+totalCalories);
        System.out.println("The percentage of each nutrient form the total amount of calories is as follows:");
        System.out.println("Carbohydrates make "+percentCarbs + "\t\tFats make "+percentFat + "\t\tProteins make "+percentProtein);
        
        if(tempRatio >= ratio){
            ratio = tempRatio;
            id = tempId;
            age = tempAge;
        }
    }

    public static int TotalGrams(int x, int y, int z){
        return (x + y + z);
    }
    
    public static int TotalCalories(int x, int y, int z){
        return (x*4) + (y*9) + (z*4);
    }
    
    public static double Percentage(int x, int y){
        return (double)x / y * 100;
    }
    
    public static double ProteinEnergyRatio(int x, int y, int z){
        return z / (x + y);
    }

}

Answer 1

我不确定我是否理解正确，但据我了解，您希望每次用户输入时都进行评估，以决定是退出应用程序还是继续旅程。如果是这种情况，您可以在请求用户输入并在该函数内做出决定的地方扩展函数。像这样：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class test{
    public static void main(String[] args){
        int id;
        int tempId;
        int age;
        int tempAge;
        int carbs;
        int fat;
        int protein;
        int totalGrams;
        int totalCalories;
        int sumGrams = 0;
        int sumCalories = 0;
        
        double percentCarbs;
        double percentFat;
        double percentProtein;
        double ratio = 0;
        double tempRatio;
        
        Scanner in = new Scanner (System.in);
        
        while(true){
            System.out.print("Please enter your ID:");
            tempId = nextInt(in);
            
            
            System.out.print("Please enter your age:");
            tempAge = nextInt(in);
            
            System.out.print("Please enter the amount of carbohydrates consumed (in grams):");
            carbs = nextInt(in);
            
            System.out.print("Please enter the amount of fat consumed (in grams):");
            fat = nextInt(in);
            
            System.out.print("Please enter the amount of protein consumed (in grams):");
            protein = nextInt(in);
            
            totalGrams = TotalGrams(carbs, fat, protein);
            totalCalories = TotalCalories(carbs, fat, protein);
            
            sumGrams += totalGrams;
            sumCalories += totalCalories;
            
            percentCarbs = Percentage(carbs*4, totalCalories);
            percentFat = Percentage(fat*9, totalCalories);
            percentProtein = Percentage(protein*4, totalCalories);
            
            tempRatio = ProteinEnergyRatio(carbs, fat, protein);
            
            System.out.println("\nThe total number of Grams consumed is "+totalGrams +" and the total number of Calories consumed is "+totalCalories);
            System.out.println("The percentage of each nutrient form the total amount of calories is as follows:");
            System.out.println("Carbohydrates make "+percentCarbs + "\t\tFats make "+percentFat + "\t\tProteins make "+percentProtein);
            
            if(tempRatio >= ratio){
                ratio = tempRatio;
                id = tempId;
                age = tempAge;
            }
        }
    }

    public static int nextInt(Scanner in){
        int val = in.nextInt();
        if(val == -1)
            System.exit(0);
        return val;
    }

    public static int TotalGrams(int x, int y, int z){
        return (x + y + z);
    }
    
    public static int TotalCalories(int x, int y, int z){
        return (x*4) + (y*9) + (z*4);
    }
    
    public static double Percentage(int x, int y){
        return (double)x / y * 100;
    }
    
    public static double ProteinEnergyRatio(int x, int y, int z){
        return z / (x + y);
    }

}

因为您询问如何才能跳出循环，所以我将为这种情况添加另一个解决方案。有多种方法可以实现这一点，但我认为使用异常在任何编程语言中都非常强大，并且可以使您的代码看起来更加清晰易懂。

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class test{
    public static void main(String[] args){
        int id;
        int tempId;
        int age;
        int tempAge;
        int carbs;
        int fat;
        int protein;
        int totalGrams;
        int totalCalories;
        int sumGrams = 0;
        int sumCalories = 0;

        double percentCarbs;
        double percentFat;
        double percentProtein;
        double ratio = 0;
        double tempRatio;

        Scanner in = new Scanner (System.in);

        while(true){
            try {
                System.out.print("Please enter your ID:");
                tempId = nextInt(in);


                System.out.print("Please enter your age:");
                tempAge = nextInt(in);

                System.out.print("Please enter the amount of carbohydrates consumed (in grams):");
                carbs = nextInt(in);

                System.out.print("Please enter the amount of fat consumed (in grams):");
                fat = nextInt(in);

                System.out.print("Please enter the amount of protein consumed (in grams):");
                protein = nextInt(in);

                totalGrams = TotalGrams(carbs, fat, protein);
                totalCalories = TotalCalories(carbs, fat, protein);

                sumGrams += totalGrams;
                sumCalories += totalCalories;

                percentCarbs = Percentage(carbs*4, totalCalories);
                percentFat = Percentage(fat*9, totalCalories);
                percentProtein = Percentage(protein*4, totalCalories);

                tempRatio = ProteinEnergyRatio(carbs, fat, protein);

                System.out.println("\nThe total number of Grams consumed is "+totalGrams +" and the total number of Calories consumed is "+totalCalories);
                System.out.println("The percentage of each nutrient form the total amount of calories is as follows:");
                System.out.println("Carbohydrates make "+percentCarbs + "\t\tFats make "+percentFat + "\t\tProteins make "+percentProtein);

                if(tempRatio >= ratio){
                    ratio = tempRatio;
                    id = tempId;
                    age = tempAge;
                }
            } catch (Exception e) {
                System.err.println(e.getMessage());
                break;
            }
        }
    }

    public static int nextInt(Scanner in) throws Exception{
        int val = in.nextInt();
        if(val == -1)
            throw new Exception("Invalid Input");
        return val;
    }

    public static int TotalGrams(int x, int y, int z){
        return (x + y + z);
    }

    public static int TotalCalories(int x, int y, int z){
        return (x*4) + (y*9) + (z*4);
    }

    public static double Percentage(int x, int y){
        return (double)x / y * 100;
    }

    public static double ProteinEnergyRatio(int x, int y, int z){
        return z / (x + y);
    }

}

当用户在循环内的任何输入中输入 -1 时如何停止 Java 程序？

How to stop Java program when the user enters -1 into any inputs inside a loop?

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