连续提示输入一个数字，直到该值落在一个范围内

Question

我有一些代码要求即将到来的派对的客人数量并返回客人数量。我应该编辑它以使其持续提示客人数量，直到值介于5和100之间。

这是我目前获取客人人数的方法。

public static int getNumberOfGuests()
{
    Scanner inputDevice = new Scanner(System.in);
    System.out.print("Please enter the number of guests >> ");
    return inputDevice.nextInt();
}

我很新，并尽力去理解。我不确定我应该使用哪个循环仍然允许返回的访客数量。

Answer 1

作为@ user7提及，您可以使用do-while次迭代来做出“直到决定”。

为什么do-while而不是常规while？因为它会在检查表达式之前执行第一次迭代。

根据您的示例，代码为：

getNumberOfGuests：

import java.util.Scanner;

public class TestGetNumGuest {

    public static void main(String[] args) {
        Scanner inputDevice = new Scanner(System.in);
        getNumberOfGuests(inputDevice);
        System.out.println("ended");
        getNumberOfGuests(inputDevice);
        System.out.println("ended");
        inputDevice.close();
    }

    public static int getNumberOfGuests( Scanner inputDevice)
    {
        int numGuests;

        do{
            System.out.print("Please enter the number of guests >> ");
            numGuests = inputDevice.nextInt();

        }while(numGuests < 5 || numGuests > 100);
        return numGuests;
    }

}

PS Scanner由getNumberOfGuests()处理，因为它应该关闭，但是如果你在方法中关闭它，你将无法多次调用

示例I / O：

Please enter the number of guests >> 1
Please enter the number of guests >> 2
Please enter the number of guests >> 3
Please enter the number of guests >> 4
Please enter the number of guests >> 6
ended
Please enter the number of guests >> 1
Please enter the number of guests >> 2
Please enter the number of guests >> 3
Please enter the number of guests >> 101
Please enter the number of guests >> 100
ended

Answer 2

一个简单的do-while或while循环将完成这项工作：

class Demo{

    public static void main(String[]args){
        try(java.util.Scanner sc = new java.util.Scanner(System.in)){
            System.out.printf("No. of guest: %d%n", getNumberOfGuests(sc,5,100));
            System.out.printf("No. of guest: %d%n", getNumberOfGuests(sc,10,19));
        }
    }

    public static int getNumberOfGuests(final java.util.Scanner sc, final int min, final int max) {
        int guest = -1;
        do{
            System.out.printf("Please enter no. of guest (%d to %d): ", min, max);
            if(sc.hasNextInt()){
                guest = sc.nextInt();
                continue;
            }
            System.out.println("Kindly input numbers only!");
            sc.nextLine();
        }while(min > guest || max < guest);
        return guest;
    }
}