4 Different ways of Reading a text file in Java (CSV Files)

In this post, We will learn very basic program How to read a file in Java. Very useful scenario which is prominently used in our real time projects.
How to read csv file in java. This is a common use case.

java.io package has utility classes for reading and writing files.

We can do reading a file in java 4 ways.

1) Using BufferedReader
2) Using JDK 7 try-with-resources
3) Using Files.readAllBytes
4) Using Files.readAllLines

First, Create a csv file with the following data in your computer(File name : employee.csv).

100,Jhon,20
101,Cena,24
102,Mike,19

 

1) Using BufferedReader:

This is very classic method to read a file using BufferedReader, FileReader. We will read the csv file using BufferedReader api and prints values of Id, Name, Age from csv file.

package com.adeepdrive.arraylist;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadingFile {

    public static void main(String[] args) {
        // file name
        String FILE_NAME = "D:\\adeepdrive\\employee.csv";

        BufferedReader br = null;
        FileReader fr = null;

        try {

            fr = new FileReader(FILE_NAME);
            br = new BufferedReader(fr);

            String currentLine;

            while ((currentLine = br.readLine()) != null) {
                String[] values = currentLine.split(",");
                System.out.println("Id: " + values[0] + ", Name: " + values[1] + ", Age: " + values[2]);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {

            try {

                if (br != null)
                    br.close();

                if (fr != null)
                    fr.close();

            } catch (IOException ex) {
                ex.printStackTrace();
            }

        }

    }
}


Output:

Id: 100, Name: Jhon, Age: 20
Id: 101, Name: Cena, Age: 24
Id: 102, Name: Mike, Age: 19

FILE_NAME holds file name and location of csv file. This can be flat file or csv file.
BufferedReader class has a method to read the file content line by line using readLine() method.
File reading operation throws IOException. So, we have put the code in try and catch block.

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2) Using JDK 7 try-with-resources:

The same above program is rewritten in java 7 using try with resources concept which closes the  br and fr automatically implicitly.

       

 String FILE_NAME = "D:\\adeepdrive\\employee.csv";
        try (BufferedReader br = new BufferedReader(new FileReader(FILE_NAME))) {

            String currentLine;

            while ((currentLine = br.readLine()) != null) {
                String[] values = currentLine.split(",");
                System.out.println("Id: " + values[0] + ", Name: " + values[1] + ", Age: " + values[2]);
            }

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

Output:

Id: 100, Name: Jhon, Age: 20
Id: 101, Name: Cena, Age: 24
Id: 102, Name: Mike, Age: 19

3) Using Files.readAllBytes

Files is a class that consists exclusively of static methods that operate on files, directories, or other types of files.
Files has a static method readAllBytes(Path path). This method reads entire file content at once and stores in String.

Static in Java.

package com.adeepdrive.arraylist;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class ReadingFiles {

    public static void main(String[] args) throws IOException {
        // file name
        String FILE_NAME = "D:\\adeepdrive\\employee.csv";
        String content = new String(Files.readAllBytes(Paths.get(FILE_NAME)));
        System.out.println("CSV File Content : ");
        System.out.println(content);
    }
}

Output:

CSV File Content :
100,Jhon,20
101,Cena,24
102,Mike,19

4) Using Files.readAllLines:

Method readAllLines(Path path) returns list which stores all lines. Reading file in Java.

   

 String FILE_NAME = "D:\\adeepdrive\\employee.csv";
        List<String> content = Files.readAllLines(Paths.get(FILE_NAME));
        System.out.println("CSV File Content : ");
        for (String line : content) {
            String[] values = line.split(",");
            System.out.println("Id: " + values[0] + ", Name: " + values[1] + ", Age: " + values[2]);
        }
        

Output:

CSV File Content :
Id: 100, Name: Jhon, Age: 20
Id: 101, Name: Cena, Age: 24
Id: 102, Name: Mike, Age: 19

Files.readAllBytes

Files.readAllLines