Question

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class Lab8 {    
public static void main(String[] args) throws IOException {

    String line, filename = "input.txt";
    FileReader fp = new FileReader("input.txt");
    Scanner scan = new Scanner(fp);
    while(scan.hasNextLine())
    {
        line=scan.nextLine();
        System.out.println(line);

    }
    int [][] matrix = new int [3][5];

    for(int i = 0; i<3; i++) 
    {
        for (int j = 0; j<5; j++)
        {

            matrix[i][j] = Integer.parseInt(scan.nextLine());
        }
    }

    for(int i = 0; i<3; i++)
    {
        //declare a sum variable and initialize to zero
        int sum = 0;
        for(int j = 0; j<5; j++)
        {

            sum +=scan.nextInt(sum);
        }
        //Compute the average of j-th quiz for all students
        //Print the sum of all quizzes for the i-th student 
        System.out.println("Total Quiz result for student 1 is ");
        System.out.println("Total Quiz result for student 2 is ");
        System.out.println("Total Quiz result for student 3 is ");
        System.out.println("Total Quiz result for student 4 is ");
    } 


    for(int j=0; j<5; j++)
    {

        int sum=0;

        for(int i=0; i<3; i++)
        {
            //update sum of j-th quiz
            //by adding the score of i-th student

        }
        //Compute the average of j-th quiz for all students
        //print the average corrected to two decimal places
        System.out.println("Average of Quiz 1 is ");
        System.out.println("Average of Quiz 2 is ");
        System.out.println("Average of Quiz 3 is ");
        System.out.println("Average of Quiz 4 is ");
        System.out.println("Average of Quiz 5 is ");

    } scan.close();
 }

}

在开始之前，我想指出我是java编码的新手。我从中获得的唯一输出是input.txt文件中的内容：10 9 10 8 7 7 8 9 8 10 6 7 8 9 10 然后错误提示：线程“main”中的异常java.util.NoSuchElementException：找不到行。任何帮助是极大的赞赏。以下代码的输出应如下所示：

从文本文件中读取用户输入学生1的总测验结果为44总测验结果为学生2为42总测验结果为学生3为40平均测验1为7.67 测验2的平均值是8.00测验3的平均值是9.00测验4的平均值是8.33测验5的平均值是9.00

Answer 1

问题是您多次使用Scanner对象来读取文件中的输入。当您使用nextInt()或nextLine()时，指针向前移动并达到EOF。因此，要重置指针，只需关闭文件资源并重新打开即可再次读取它。

我编辑了你的代码：

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class Lab8 {    
public static void main(String[] args) throws IOException {

    String line, filename = "input.txt";
    FileReader fp = new FileReader("input.txt");
    Scanner scan = new Scanner(fp);
    /*while(scan.hasNextLine()) // -> Instead of printing here, print in the for loop below
    {
        line=scan.nextLine();
        System.out.println(line);

    }*/
    int [][] matrix = new int [3][5];

    for(int i = 0; i<3; i++) 
    {
        for (int j = 0; j<5; j++)
        {

            line=scan.nextLine();
            System.out.println(line);  // print here.
            matrix[i][j] = Integer.parseInt(line);
        }
    }
    scan.close();                      // close the scanner
    fp.close();                        // close the file reader
    fp = new FileReader("input.txt");  // reopen file reader
    scan = new Scanner(fp);            // reopen scanner

    for(int i = 0; i<3; i++)
    {
        //declare a sum variable and initialize to zero
        int sum = 0;
        for(int j = 0; j<5; j++)
        {
            sum +=scan.nextInt();
        }
        //Compute the average of j-th quiz for all students
        //Print the sum of all quizzes for the i-th student 
        System.out.println("Total Quiz result for student 1 is ");
        System.out.println("Total Quiz result for student 2 is ");
        System.out.println("Total Quiz result for student 3 is ");
        System.out.println("Total Quiz result for student 4 is ");
    } 


    for(int j=0; j<5; j++)
    {

        int sum=0;

        for(int i=0; i<3; i++)
        {
            //update sum of j-th quiz
            //by adding the score of i-th student

        }
        //Compute the average of j-th quiz for all students
        //print the average corrected to two decimal places
        System.out.println("Average of Quiz 1 is ");
        System.out.println("Average of Quiz 2 is ");
        System.out.println("Average of Quiz 3 is ");
        System.out.println("Average of Quiz 4 is ");
        System.out.println("Average of Quiz 5 is ");

    } scan.close();
 }

}

关闭Scanner对象是不够的。您必须关闭FileReader对象才能重置文件中的指针。

我希望它对你有所帮助。

我正在尝试从input.txt文件中读取内容，将它们存储在2D数组中，打印数组内容

1 个答案: