从文本文件创建二维数组并求平均值

Question

I'm trying to create a 2D array from numbers in a text file, that can be printed and the average is found of each column. Note: I get an error saying "Type mismatch: cannot convert from java.lang.String to int" on "int rows" and "int columns". Any feedback would be much appreciated.

Example Text File:

3

4

6 4 2 12

3 5 6 0

11 0 3 0

Example Output:

Array of scores:

[6, 4, 2, 12]

[3, 5, 6, 0]

[11, 0, 3, 0]

Average score of each assignment:

Assignment #1 Average: 6.66666666666

Assignment #2 Average: 9.0

Assignment #3 Average: 3.66666666666

Assignment #4 Average: 4.0

import java.util.Scanner;
import java.io.File;  
import java.io.FileNotFoundException; 
import java.util.Arrays;

public class Scores {
  public static void main(String[] args) throws FileNotFoundException {
    Scanner keyboard = new Scanner(System.in);
    System.out.println("What is the name of the file containing the scores?");
    String fileName = keyboard.nextLine();
    Scanner fileScan = new Scanner(new File(fileName));

    //TODO: read in the values for the number of students and number of assignments using the Scanner on the file
    //TODO: create a 2-D to store all the scores and read them all in using the Scanner on the file
    int rows = fileScan.nextLine();
    int columns = fileScan.nextLine();

    int [][] myArray = new int[rows][columns];
      while(fileScan.hasNextLine()) {
         for (int i=0; i<myArray.length; i++) {
            String[] line = fileScan.nextLine().trim().split(" ");
            for (int j=0; j<line.length; j++) {
               myArray[i][j] = Integer.parseInt(line[j]);
            }
         }
      }


    System.out.println("Array of scores:");
    //TODO: print the entire array, row by row, using Arrays.toString()
    System.out.println(Arrays.deepToString(myArray));

    System.out.println("Average score of each assignment:");
    //TODO: compute and print the average on each assignment
   double total=0;
    int totallength,assignment;
    for(int i=0;i<myArray.length;i++) {
        for(int j=0;j<myArray[i].length;j++) {
            total+=myArray[i][j];
            totallength++;
        System.out.println("Assignment #" + assignment++ + " Average: " + (total/totallength));
        }
    }
    fileScan.close(); 
  }
}

Answer 1

Scanner.nextLine() returns a String, not an int. You can try something like int rows = fileScan.nextInt() or int rows = Integer.parseInt(fileScan.nextLine());

Answer 2

Your problem is that rows and columns are Strings when you read them from the file. You need to convert them to Integers before you can use them as array indices. So do something like this:

int rows = Integer.parseInt(fileScan.nextLine());
int columns = Integer.parseInt(fileScan.nextLine());