按列读取文本文件并在Java中创建2d数组

Question

How do I read the below text file by column, and find the min value for the grade array by column? Thanks in advance for your help.

This is my text file

John  25 5 4.5 5 4 5 10 10 6 9.5 5.5
Jim   25 5 4 5 4.5 5 10 4 10 9.5 7.5
Kathy 15 1 3 2 1 1.5 8 2 4 3 4
Steve 21 5 3 2 1 4 5 6 7 8 8
Stacy 15 5 1 1 1 5 3 8 9 5 7
Faith 16 3 4 2 4 4 7 5 2 3 8

This is what I want the array to look like

Name = John, Jim, Kathy, Steve, Stacy, Faith
grade1 = 25 25 15 21 15 16
grade2 = 5 5 1 5 5 3
grade3 = 4.5 4 3 3 1 4

and so on ....

This is my code

public static void main(String[] arg) throws IOException
{
    PrintWriter writer =  new PrintWriter(new FileOutputStream("Output.txt"));

    double[][] grades = null;

    findMinIndex(grades); //I call the function here just to test out my result before print out to text file.

     writer.println("Min: " + findMinIndex(grades));
     writer.close();
}

//This method to read the file -- have to add this part or the page wont' let me save my code --

public static void processSection(PrintWriter writer, double[][]grades, String[] names) throws IOException
{
{
    Scanner in  = null;

    try
    {
        in = new Scanner(new FileInputStream("input.txt"));         

        //in.nextLine();

          int rows = in.nextInt();
          int columns = in.nextInt();             
          grades = new double[rows][columns];             
          names = new String[grades.length];    
          String[] col = null;

          while(in.hasNextLine()) 
          {     
              for (int i=0; i< grades.length; i++)
              {
                  col = in.nextLine().trim().split("\\s+");     

                  for (int j = 1; j < col.length; j++)                     
                  {                              
                      names[i] = col[0];

                      grades[i][j] = Double.parseDouble(col[j]);

                  }   
              }         
          }  

         in.close();     
    }

    catch(Exception e)
    {

    }

}

//This method to find Min
public static double findMinIndex(double[][] grades) throws FileNotFoundException, IOException 
{       
        double min = grades[0][0];  

        for (int j = 0; j < grades.length; j++) 
        {
            min = Integer.MAX_VALUE;

            for (int i = 1; i < grades[j].length; i++) 
            {                                       
                if (grades[j][i] < min) 
                {                   
                    min = grades[j][i];                      
                }
            }               
        }

        System.out.println(min);
        return min;
}

//The result I got is to calculate the min by the row not by the column.

Answer 1

import java.io.IOException;
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.List;
import java.util.Arrays;

class Create2DArray {

    public static void main(String[] arg) throws IOException {
        String[] names = getNames();
        List namesArrayList = Arrays.asList(names);
        String stringNames = namesArrayList.toString()
                .replace("[", "")
                .replace("]", "")
                .trim();         

        double[][] grades = getGrades();

        System.out.println("Name = " + stringNames);

        double rowsum = 0;
        for (int i = 0; i < grades[0].length; i++) {
            System.out.print("grade" + (i+1) + " = ");
            for (int j = 0; j < grades.length; j++) {
                System.out.print(grades[j][i] + " ");
                rowsum += grades[j][i];
            }
            System.out.println("; Row sum = " + rowsum);
            rowsum = 0;
        }
    }

    private static String[] getNames() throws IOException {
        String[] names = null;

        BufferedReader buffer = new BufferedReader(new FileReader("input.txt"));

        String line;
        int row = 0;
        int size = 0;

        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
        int lines = 0;
        while (reader.readLine() != null) lines++;
        reader.close();

        while ((line = buffer.readLine()) != null) {
            String name = line.trim().split("\\s+")[0];

            if (names == null) {
                size = lines;
                names = new String[size];
            }

            names[row] = name;
            row++;
        }
        return names;
    }

    private static double[][] getGrades() throws IOException {
        double[][] matrix = null;

        BufferedReader buffer = new BufferedReader(new FileReader("input.txt"));

        String line;
        int nrows = 0;
        int row = 0;
        int ncols = 0;

        while (buffer.readLine() != null) nrows++;
        buffer.close();

        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));

        while ((line = reader.readLine()) != null) {
            String[] vals = line.trim().split("\\s+");
            ncols = vals.length-1;

            if (matrix == null) {
                matrix = new double[nrows][ncols];
            }

            for (int col = 1; col <= ncols; col++) {
                try {
                    matrix[row][col-1] = Double.parseDouble(vals[col]);
                }
                catch (NumberFormatException e) {}
            }
            row++;
        }
        reader.close();
        return matrix;
    }
}

output:

Name = John, Jim, Kathy, Steve, Stacy, Faith
grade1 = 25.0 25.0 15.0 21.0 15.0 16.0 ; Row sum = 117.0
grade2 = 5.0 5.0 1.0 5.0 5.0 3.0 ; Row sum = 24.0
grade3 = 4.5 4.0 3.0 3.0 1.0 4.0 ; Row sum = 19.5
grade4 = 5.0 5.0 2.0 2.0 1.0 2.0 ; Row sum = 17.0
grade5 = 4.0 4.5 1.0 1.0 1.0 4.0 ; Row sum = 15.5
grade6 = 5.0 5.0 1.5 4.0 5.0 4.0 ; Row sum = 24.5
grade7 = 10.0 10.0 8.0 5.0 3.0 7.0 ; Row sum = 43.0
grade8 = 10.0 4.0 2.0 6.0 8.0 5.0 ; Row sum = 35.0
grade9 = 6.0 10.0 4.0 7.0 9.0 2.0 ; Row sum = 38.0
grade10 = 9.5 9.5 3.0 8.0 5.0 3.0 ; Row sum = 38.0
grade11 = 5.5 7.5 4.0 8.0 7.0 8.0 ; Row sum = 40.0