CSV to tab delimited java in command line

Question

Updated Code. This program should take the CSV file and separate it into TSV files by school,but I am not getting it to work. I am getting it to create the files correctly, but only one has any data in it...

public class Student implements Comparable<Student>{

    public int id = 0;
    public String name = "";
    public String school = "";


    public Student(int id, String name, String school){

        this.id = id;
        this.name = name;
        this.school = school;
    }

    public String toString(){
        return id+"\t"+name+"\t"+school;
    }

    @Override
    public int compareTo(Student o) {
        return  this.school.compareTo(o.school);
    }
}

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;


public class ReadCSV {

    public static String CSV_FILE_PATH = "/Users/eringray/Desktop/csvtotab/input.csv";

    public static void main(String[] args){

        try {

            BufferedReader br = new BufferedReader(new FileReader(CSV_FILE_PATH));
            BufferedWriter bw = new BufferedWriter(new FileWriter(CSV_FILE_PATH + ".tsv"));

            ArrayList<Student> list = new ArrayList<Student>();

            String line = "";
            while((line = br.readLine()) != null) {
                String[] values = line.split(",");

                if(values.length == 3) {
                    String idAsString = values[0];
                    String name = values[1];
                    String school = values[2];

                    int id = Integer.parseInt(idAsString);

                    Student s = new Student(id, name, school);

                    list.add(s);
                }
            }

            Collections.sort(list);

            String currentSchool = "";
            for(int i = 0; i < list.size(); i++){
                Student stu = list.get(i);
                if(currentSchool != stu.school){
                  currentSchool = stu.school; 
                  bw = new BufferedWriter(new FileWriter(CSV_FILE_PATH + stu.school + ".tsv"));
              }

              String lineText = stu.toString();
              bw.write(lineText);
              bw.newLine();
            }

            br.close();
            bw.close();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

Do you really need to use java for this, using the linux utility tr is quicker as it can do tr ',' '\t' to replace them really quick — Ferrybig
– Ferrybig, Commented Jan 22, 2016 at 15:28
yeah, I need to use java, this is an assignment I'm working on. thanks! — Rassisland
– Rassisland, Commented Jan 22, 2016 at 15:30
do you allready have some code? please post it, if so. What you need, is the replace function of the string class: docs.oracle.com/javase/7/docs/api/java/lang/… — Jarlik Stepsto
– Jarlik Stepsto, Commented Jan 22, 2016 at 15:32
I feel like I would need something like this, but am unsure of how to change the variables to make it do what I want to on different files. coderanch.com/t/592700/java/java/… — Rassisland
– Rassisland, Commented Jan 22, 2016 at 15:37
read my answer, but if you dont have to sort the list by school, but only replace the , by tabs, you can read the file (bufferedreader) line by line, use the replace method on the line (to replace , by \t) and write the output line in a new file (bufferedwriter). for more details, read my answer — Jarlik Stepsto
– Jarlik Stepsto, Commented Jan 22, 2016 at 15:47

Jarlik Stepsto · Accepted Answer · 2016-01-22 15:42:57Z

2

The first thing, you have to do is reading the input file. I think, you need to read it line by line (depends on file structure).

https://docs.oracle.com/javase/7/docs/api/java/io/FileInputStream.html

https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html

Next step is to seperate the data and sort it by school (if i understood your question well).

For this you have to split the data and create a class to store the information:

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)

public Class Student{
   public String name = "";
   ....

   public Student(String name, String school, ...){}
}

When you have created a Student object for each student in the list, you have to sort the students by school:

You could implement compareable and use Collection.sort().

https://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html

Last thing is to print the output, for this you have to override the toString method of the student class:

public String toString(){
   return this.id+"\t"+this.name+"\t"+this.school;
}

and iterate throug the list of your students and call the toString method:

System.out.println(students.get(i).toString());

EDIT:

If you need the output in a file and not in the console, just use a fileoutputStream and a bufferedwriter to print the output of the toString method in a file.

answered Jan 22, 2016 at 15:42

Jarlik Stepsto

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16 Comments

Rassisland Over a year ago

Awesome! That is exactly what I was looking for! I'll give that a shot and may return with a few small questions. Thanks again!

Rassisland Over a year ago

I've been working on this over the weekend but have been struggling. I've added what I have so far to my original post. For the next step, am I supposed to create a new java class file? How could I get that to work with my original code? Sorry for the novice questions, I just started learning java last week, so I am quite behind!

Rassisland Over a year ago

the assignment is to do it in a text editor, but I don't really understand how to do it that way

Jarlik Stepsto Over a year ago

ok, i will write you same code and explanaition (should take about 10 mins)

Jarlik Stepsto Over a year ago

@Rassisland so, i have written some code, with comments. At first, create a folder, for your code, then create to text files and name them: Person.java and Test35.java ---- you can change the names, but then you should also change the class names. The code is here: pastebin.com/aYJj1AQk and pastebin.com/avC7vqzx The last think you need, is to change path to your file and then compile the whole think: go on commandline into the folder, with your java files and do javac *.java to compile all the files and java Test35 to run the main method of the programm.

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