我试图从input.txt文件读取内容，将它们存储在二维数组中，打印数组内容

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(); 
} 

} 

在我开始之前，只想指出我是java编码的新手。我从这个得到的唯一输出是从input.txt中文件中的内容：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。以下代码的输出应该如下所示：

用户输入从文本文件中读取 学生1的总测验结果是44学生2的总测验结果是42学生3的总测验结果是40测验的平均值图1是7.67 平均测验2的是8.00平均测验3的是9.00平均测验4的是8.33平均测验5的是9.00

Answer 1

的问题是使用的是Scanner对象多次读取来自文件的输入。当您使用nextInt()或nextLine()时，指针向前移动并达到EOF。因此，重置指针只需关闭文件资源并重新打开即可重新读取。

我编辑您的代码：

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。