Unable to read data from file in java

Question

I am working in java code to read data from a text file and print the data in another text file. I didn't have any errors, but when I run it shows like there is no input and all I got was this as output and an empty file (in the printwriter file). But, I am pretty sure that there is input in the file that I read using the scanner.

 Process finished with exit code 0

This is my code:

import java.io.*;
import java.util.Scanner;
public class ASSI4 {
    public static void main(String[] args) {
        try {
            Scanner kbd = new Scanner(new File("st.txt"));
            PrintWriter nbb = new PrintWriter((new File("res.txt")));
            long[] ID = new long[30];
            double[][] CM = new double[30][6];
            while (kbd.hasNextLine()) {
                for (int i = 0; i < 30; i++) {
                    String line = kbd.nextLine();
                    String[] arr = line.split("\t");
                    ID[i] = Long.parseLong(arr[0]);

                    {
                        CM[i][0] = Double.parseDouble(arr[1]);
                        CM[i][1] = Double.parseDouble(arr[2]);
                        CM[i][2] = Double.parseDouble(arr[3]);
                        CM[i][3] = Double.parseDouble(arr[4]);
                        CM[i][4] = Double.parseDouble(arr[5]);
                        CM[i][5] = Double.parseDouble(arr[6]);
                    }
                }

                for (int i = 0; i < 30; i++) {
                    double sumA = 0;
                    for (int j = 0; j < 6; j++) {
                        sumA = sumA + CM[i][j];
                    }
                    double avg = sumA / 6;
                    avg = Math.round(avg * 100.0) / 100.0;
                    nbb.println(ID[i] + "  " + CM[i][0] + "  " + CM[i][1] + "  " + CM[i][2] + "  " + CM[i][3] + "  " + CM[i][4] + "  " + CM[i][5] + " " + avg);
                }
            }
            nbb.close();
            kbd.close();


        }
        catch (Exception e) {
            e.getMessage();
        }
    }
}

This is my st.txt file:

20186966 90.0 55.8 98.0 67.9 46.0 77.1
20185978 32.0 19.8 49.8 67.0 86.4 46.0
20189409 53.8 79.0 84.6 39.9 74.5 27.0
20183970 39.7 88.0 78.6 66.0 25.4 0.0
20190291 36.9 32.8 10.0 46.8 21.5 65.9 
20196949 99.0 47.6 36.7 85.5 82.9 77.0
20173040 46.8 40.9 30.5 95.9 94.9 99.8 
20171679 55.7 29.0 99.8 36.8 69.0 80.6 
20175747 77.0 100.0 56.7 36.9 34.8 22.9 
20190850 84.0 85.5 68.8 81.7 83.9 57.8 
20193406 20.0 44.5 50.0 18.6 30.9 77.8 
20175802 71.9 80.0 60.8 99.9 31.0 87.9 
20184693 46.0 94.9 58.7 73.0 35.7 29.5
20185769 76.9 67.8 51.8 12.6 96.0 94.0
20181274 28.9 85.9 76.6 42.9 32.0 95.9
20194284 1.0 44.8 75.6 44.8 33.9 30.6
20175501 70.9 24.5 48.8 80.5 76.8 61.9
20198125 6.0 16.0 12.9 25.0 3.0 29.6
20194027 33.0 27.7 83.9 31.0 75.0 74.9
20179253 87.0 100 22.9 68.9 14.8 98.0
20172010 94.0 93.9 31.9 100 70.8 90.0
20177254 11.0 26.5 2.6 30.8 86.0 100.0
20184917 60.9 24.3 49.6 61.9 66.0 80.9
20181322 83.0 45.3 74.5 64.5 50.0 99.7
20196820 78.0 75.0 70.9 56.9 99.0 19.9
20196734 35.4 34.9 84.8 68.0 15.9 70.0
20192018 91.0 59.5 3.4 42.9 81.0 58.8
20178007 55.9 94.8 71.5 38.0 81.7 98.0
20173948 93.0 100.0 9.8 45.7 47.0 9.9
20192749 26.0 45.0 57.4 95.9 14.4 79.0

Can you show examples of input file and output expectations? — Bradley, May 18 '20 at 21:25
Does this answer your question? [Reading a plain text file in Java](https://stackoverflow.com/questions/4716503/reading-a-plain-text-file-in-java) — Bradley, May 18 '20 at 21:27
I suggest you to write `e.printStackTrace()` instead of `e.getMessage()` in your `catch` block. — SomeDude, May 18 '20 at 21:27
Have you stepped through it? I think the first thing to do would be to narrow down the issue. Make sure your loops are working correctly and your arrays are being populated properly. If all that's good maybe take a closer look at PrintWriter and make sure you can print concatted complex strings and stuff. — ARC, May 18 '20 at 22:00
e.printStackTrace() , i try this and it give me the same problem with errors — Mry, May 18 '20 at 22:26
@Mry - I tested my code with the content which you have posted and it worked perfectly. What's the problem you are facing? I suggest you copy my code and run it as it is. — Arvind Kumar Avinash, May 18 '20 at 23:10

Arvind Kumar Avinash · Accepted Answer · 2020-05-18T22:40:05.873

Problem:

You have used \t instead of \\s+. We should use \\s+ to match a whitespace character: [ \t\n\x0B\f\r]. Check this to learn more about patterns.

Side notes:

Follow Java naming conventions e.g. ID should be named as id and CM should be named as cm.
Do not mix reading with writing i.e. read the source file and close it and then write to the target file and close it.
Replace e.getMessage(); with e.printStackTrace(); or at least System.out.println(e.getMessage());.

Updated code:

import java.io.File;
import java.io.PrintWriter;
import java.util.Scanner;

public class ASSI4 {
    public static void main(String[] args) {
        try {
            Scanner kbd = new Scanner(new File("st.txt"));
            long[] id = new long[30];
            double[][] cm = new double[30][6];
            while (kbd.hasNextLine()) {
                for (int i = 0; i < 30; i++) {
                    String line = kbd.nextLine();
                    String[] arr = line.split("\\s+");
                    id[i] = Long.parseLong(arr[0]);
                    cm[i][0] = Double.parseDouble(arr[1]);
                    cm[i][1] = Double.parseDouble(arr[2]);
                    cm[i][2] = Double.parseDouble(arr[3]);
                    cm[i][3] = Double.parseDouble(arr[4]);
                    cm[i][4] = Double.parseDouble(arr[5]);
                    cm[i][5] = Double.parseDouble(arr[6]);
                }
            }
            kbd.close();

            PrintWriter nbb = new PrintWriter((new File("res.txt")));
            for (int i = 0; i < 30; i++) {
                double sumA = 0;
                for (int j = 0; j < 6; j++) {
                    sumA = sumA + cm[i][j];
                }
                double avg = sumA / 6;
                avg = Math.round(avg * 100.0) / 100.0;
                nbb.println(id[i] + "  " + cm[i][0] + "  " + cm[i][1] + "  " + cm[i][2] + "  " + cm[i][3] + "  "
                        + cm[i][4] + "  " + cm[i][5] + " " + avg);
            }
            nbb.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Unable to read data from file in java

1 Answers1

Problem:

Updated code: