Read a csv data file and reutrn one specific StudentID marks for all their modules in Java

Question

Hi, at the moment I have this:

import java.util.*;
import java.io.*;
import java.io.BufferedReader;
import java.io.FileReader;

public class StudentID {

  public static void main(String[] args)throws Exception{

   System.out.println ("Please enter StudentID: ");
   BufferedReader reader = new BufferedReader (new FileReader("CW2_data.csv"));
      File file = new File("CW2_data.csv");
 try {
    BufferedReader r = new BufferedReader(
                        new InputStreamReader(
                        new FileInputStream("CW2_data.csv")));
    String line;
    while((line = r.readLine()) != null)
        System.out.println(line);
    r.close();
} catch(IOException e) {
    System.out.println(" There was an Error Reading the file. " + e.getMessage());
}


  }
}

I am trying to get the program to prompt the user for its StudentID, then search through the data file for that StudentId and return their marks for all the modules. Unfortunatly all my codes does is list the whole file back to me.

I tried to add StudetnID=Userinput.readstring; right after so that user was given an opertunity to type in the username but then I realise that wouldn't work unless I tell it scan the whole document for it. I was reading up on maps (as recomendeded by user on here) but I still haven't got to grips with it and I don't know if it would it even work here. The data file is in form of 3 columns and about 282 rows of data, ie

UserID: Module: Mark

ab006, GYH095, 56

Any help would appreciated.

Answer 1

As that this appears to be homework (and how it relates to your previous question) I will not give a full solution.

The buffered reader reads an entire line of text. So you'll get strings similar to this: "ab006, GYH095, 56"

With that string you can use something like StringTokenizer or String.split to seperate the individual elements, which now become "ab06", "GYH095", "56" ...

The reason this program just writes the entire file back to you is that the program just scans through the file, without doing anything to what it reads.

Answer 2

Well, it is good progress that you are getting the file to be read properly. What you first want to do is get the user's input before reading the file. This can be done with the Java Scanner class. Take a look there for examples on how to use it (you will want to read a String from the user. Hint: the nextLine() method). The rest can be done via stevens explanation.

Answer 3

To load the data, how about you make a simple class that represents a line from your datafile, and then store it in a List. Yes, you'll have to scan through the entire list each time but it doesn't seem that large anyway (if there is a natural key you can use, which appears to be the case, you could indeed use a Map). Check out the java tutorial on collections.

Answer 4

import java.util.*;

import java.io.*; import java.io.BufferedReader; import java.io.FileReader; import java.util.Scanner;

public class StudentID {

    public static void main(String[] args)throws Exception{
    String studentid;               // Declare a variable to hold the name.
    Scanner in = new Scanner(System.in);
    //... Prompt and read input.
    System.out.print("Please enter studentId please: ");
    studentid = in.nextLine();      // Read one line from the console.
    in.close();


    }

}

I have got it to read input from the user, that was simple enough but I cant get my head around using string split() to search for the ID. I understand it splits the file into readable chuncks but how do you get it to search for that specific ID in the txt and return the results for their mark?