如何使用CTRL D中断while循环 [英] How do I break out of a while loop with CTRL D

问题描述

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lettergrades;

import java.util.Scanner;
/**
 *
 * @author user1
 */
public class LetterGrades {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        int total = 0;
        int gradeCounter = 0;
        int aCount = 0;
        int bCount = 0;
        int cCount = 0;
        int dCount = 0;
        int fCount = 0;
        
        Scanner input = new Scanner(System.in);
        
        System.out.printf("%s%n%s%n%s%n%s%n ",
        "Enter the integer grades in the range 0-100",
        "Type the end-of-file indicator to terminate input",
        "On UNIX/LINUX/MACOS type <CMD> d then press Enter",
        "On WINDOWS type <CTRL> z then press Enter");
        
        do
        {            
            int grade = input.nextInt();
            total += grade;
            ++ gradeCounter;
            
            switch(grade/10)
            {
                case 9:
                case 10:
                    ++aCount;
                    break;
                case 8:
                    ++bCount;
                    break;
                case 7:
                    ++cCount;
                    break;
                case 6:
                    ++dCount;
                    break;
                default:
                    ++fCount;
                    break;
            }
            
        } while(input.hasNext());
        
       System.out.printf("%nGrade Report:%n");

       if (gradeCounter != 0)
       {
           double average = (double) total / gradeCounter;

           System.out.printf("Total of the %d grades entered is %d%n", gradeCounter, total);
           System.out.printf("Class average is %.2f%n", average);
           System.out.printf("%n%s%n%s%d%n%s%d%n%s%d%n%s%d%n%s%d%n", 
                   "Number of students who recieved each grade:",
                   "A: ",aCount,
                   "B: ",bCount,
                   "C: ",cCount,
                   "D: ",dCount,
                   "F: ",fCount);
       }
       else
           System.out.println("No grades were entered...");
    }
    
}

我尝试过：



我已经用JAVA程序编写了这个例子。我一直试图弄清楚为什么CTRL D不会结束循环并继续使用System.out.printf（％nGrade Report：％n）;.我尝试了不同的循环变体，它只是不起作用。如果我在循环中包含输出它可以工作，但理想情况下它只在循环外放置一次。我知道还有其他方法可以做到这一点，但我希望按照作者的意图使用它。预先感谢您的帮助。

What I have tried:

Hi, I have written this example out of JAVA HOW TO PROGRAM. I have been trying to figure out why CTRL D does not end the loop and go on to System.out.printf("%nGrade Report:%n");. I have tried different variations of loops and it just does not work. If I include the output in the loop it works, but ideally it would only run once when placed outside the loop. I know there are other ways to do this, but I would like to get this working the way the Author intended. Thanks in advance for any help.

推荐答案

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lettergrades;

import java.util.Scanner;
/**
 *
 * @author user1
 */
public class LetterGrades {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        String keepGoing = "yes";
        int total = 0;
        int gradeCounter = 0;
        int aCount = 0;
        int bCount = 0;
        int cCount = 0;
        int dCount = 0;
        int fCount = 0;
        
        Scanner input = new Scanner(System.in);
        
        System.out.printf("%s%n%s%n ",
        "Enter the integer grades in the range 0-100",
        "Enter 0 to end the program");
        
        do
        {            
            int grade = input.nextInt();
            total += grade;
            ++ gradeCounter;
            
            if(grade != 0)
            {
                switch(grade/10)
                {
                    case 9:
                    case 10:
                        ++aCount;
                        break;
                    case 8:
                        ++bCount;
                        break;
                    case 7:
                        ++cCount;
                        break;
                    case 6:
                        ++dCount;
                        break;
                    default:
                        ++fCount;
                        break;
                }
            }
            else
            {
                keepGoing = "no";
                break;
            }
            
        } while(keepGoing.equals("yes"));
        
       System.out.printf("%nGrade Report:%n");

       if (gradeCounter != 0)
       {
           double average = (double) total / gradeCounter;

           System.out.printf("Total of the %d grades entered is %d%n", gradeCounter, total);
           System.out.printf("Class average is %.2f%n", average);
           System.out.printf("%n%s%n%s%d%n%s%d%n%s%d%n%s%d%n%s%d%n", 
                   "Number of students who recieved each grade:",
                   "A: ",aCount,
                   "B: ",bCount,
                   "C: ",cCount,
                   "D: ",dCount,
                   "F: ",fCount);
       }
       else
           System.out.println("No grades were entered...");
    }
    
}

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