考试分数在 1 到 100 之间

Question

import java.util.Scanner;

public class Exercise1{
public static void main(String args[]){
    int i=1,mark,totalmarks=0,highestmark=0;

    Scanner input = new Scanner(System.in);

    do{
        System.out.print("Please enter the mark of student " + i + ":");
        mark = input.nextInt();

        while(mark<0 || mark>100)
        {
            System.out.print("Invaild! Please enter the mark of student " + i + ":");
            mark = input.nextInt();
        }
        if(mark>highestmark)
            highestmark = mark;

        totalmarks += mark;

        System.out.println("\n");

        i++;

    }while(i<=5);

    System.out.println("\n\nHighest mark was: " + highestmark +
                       "\nAverage mark was: " + String.format("%.0f",totalmarks/5f));
    }
}

在 5 名学生的考试成绩中，确定获得的最高分数以及最接近的整数的平均分数。这些标记都应该是 0 到 100 范围内的数学整数（整数）。

上面那一段就是这段代码的对象。 我想知道这段代码在逻辑上很奇怪。

如果（标记>最高标记） 最高标记 = 标记； 当我看到这段代码时，我以为所有的数字都可以是 1,2,3 到 100 这样的标记 但最高标记最初被初始化为 0。 怎么合乎逻辑？

最后一个语句是 (totalmarks/5f) 为什么我要在 5 的末尾添加“f”？ 如果我不添加 f，则会输出错误 请为我回答并解释这些问题，感谢您的帮助

Answer 1

所以最高标记被初始化为 0，因为任何标记都会高于此。这意味着第一次通过循环的最高标记将被设置为第一个标记。如果它被初始化为 1 到 100 之间的某个数字，如果所有学生的分数都低于最高分的初始值，这可能会导致错误的输出。它甚至可以设置为 -1，因为 0 是有效标记。

至于最后一条语句，它使用 5f 因为这会将值转换为除法所需的浮点数。如果两个值都是整数，java 将执行整数除法，这在这种情况下不是您想要的。

Answer 2

为了便于阅读，我对您的代码进行了一些修改，并添加了一些关于它在做什么的 cmets。我也更改了变量名和声明。有关逻辑，请直接在代码中查看 cmets。至于用于计算平均值的除法中数字末尾的f，如果缺少它，您会得到java.util.IllegalFormatConversionException 异常，因为5 的数据类型是int（而不是float）。在下面的代码中，文字 (5) 已被替换为常量 TOTAL_STUDENTS，该常量被强制转换为浮点数（参见 (float)）以执行除法。

// declare a constant for the number of students.
// this will make changes easier (avoid hard-coding constants in code).
private static final int TOTAL_STUDENTS = 5;

// these two constants are for the bounds on the mark (it
// must be between 0 and 100)
private static final int LOWEST_MARK_POSSIBLE = 0;

private static final int HIGHEST_MARK_POSSIBLE = 100;

public static void main(String args[]) {
    // you had the current student as 1 and an increment at the end of the loop
    // but if you increment at the beginning of your do loop it reads better
    int currentStudent = 0;

    // no marks have been given yet in input
    int totalMarks = 0;

    // initialize the highest mark at this point (beginning of the program) 
    // as 0 because no data has been collected yet and since all marks 
    // have to be greater than or equal to 0, this is the lowest starting 
    // mark possible
    int highestMark = LOWEST_MARK_POSSIBLE;

    Scanner input = new Scanner(System.in);

    do {
        currentStudent++;
        System.out.print("Please enter the mark of student " + currentStudent + ":");

        // get the next integer entered from the keyboard
        int currentStudentMark = input.nextInt();
        // validate it -- if it's not in the acceptable bounds, retry
        while (currentStudentMark < LOWEST_MARK_POSSIBLE || currentStudentMark > HIGHEST_MARK_POSSIBLE) {
            System.out.print("Invaild! Please enter the mark of student " + currentStudent + ":");
            currentStudentMark = input.nextInt();
        }

        // if the mark that was just entered is more than the 
        // highest mark stored, update the highest mark to 
        // be equal to the mark just entered
        if (currentStudentMark > highestMark) {
            highestMark = currentStudentMark;
        }

        // add the current student mark to the total marks counted
        totalMarks += currentStudentMark;

        System.out.println("\n");

    } while (currentStudent < TOTAL_STUDENTS); 
    // your while condition was <= 5 because you had the increment at the end of the 
    // cycle for the current student

    // this was missing in your original code; the InputStream should always be closed when you're done with it
    input.close();

    System.out.println("\n\nHighest mark was: " + highestMark + "\nAverage mark was: "
            + String.format("%.0f", totalMarks / (float) TOTAL_STUDENTS));
}