java - 确定代码的哪一部分负责使程序按照用户在测试次数中所说的去做

Question

该程序是关于提示用户输入他们想要平均多少次测试，然后程序会要求他们输入他们所说的多少。我无法确定代码是如何做到的。是什么让它知道返回用户要求的尽可能多的输入。谢谢！

我查看了 while 函数，但这似乎只有在用户输入 0 或负数（我认为）之类的东西时才会出现。

import java.util.Scanner;

public class average {

    public static String getLetterGrade(double average) {
        if (average < 60) {
            return "F";
        } else if (average < 70) {
            return "D";
        } else if (average < 80) {
            return "C";
        } else if (average < 90){
            return "B";
        }
         else;{
            return "A";
        }
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("Welcome, please type your first name. ");
        String name = scan.nextLine();
        System.out.println("Welcome, please type your last name. ");
        String last = scan.nextLine();
        int n;
        System.out.println("How many tests would you like the average of?");
        n = scan.nextInt();

        while(n<0) {
            System.out.println("Invalid input.");
            System.out.println("How many tests would you like the average 
                of?");
            n = scan.nextInt();
       }

       double sum = 0, grade;
       System.out.println("Enter " + n + " scores.");
       for(int i = 0;i<n;i++) {
           grade = scan.nextDouble();
           sum += grade;
       }
       double average = (sum/n);
       System.out.println("Okay " + name.charAt(0) + last.charAt(0) + ", your 
       average score is " + (average));
       System.out.println("Your letter grade is a " + 
       getLetterGrade(average));

    }

}

它运行的这个程序没有错误，它执行它应该做的事情。

标签： java