// Tutorial //

How To Read a File Line-By-Line in Java

Published on August 3, 2022 · Updated on November 29, 2022
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By Pankaj
Developer and author at DigitalOcean.
How To Read a File Line-By-Line in Java

Introduction

In this article, you will learn about different ways to use Java to read the contents of a file line-by-line. This article uses methods from the following Java classes: java.io.BufferedReader, java.util.Scanner, Files.readAllLines(), and java.io.RandomAccessFile.

Reading a File Line-by-Line using BufferedReader

You can use the readLine() method from java.io.BufferedReader to read a file line-by-line to String. This method returns null when the end of the file is reached.

Here is an example program to read a file line-by-line with BufferedReader:

ReadFileLineByLineUsingBufferedReader.java
package com.journaldev.readfileslinebyline;

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

public class ReadFileLineByLineUsingBufferedReader {

	public static void main(String[] args) {
		BufferedReader reader;

		try {
			reader = new BufferedReader(new FileReader("sample.txt"));
			String line = reader.readLine();

			while (line != null) {
				System.out.println(line);
				// read next line
				line = reader.readLine();
			}

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

}

Continue your learning with the BufferedReader API Doc (Java SE 8).

Reading a File Line-by-Line using Scanner

You can use the Scanner class to open a file and then read its content line-by-line.

Here is an example program to read a file line-by-line with Scanner:

ReadFileLineByLineUsingScanner.java
package com.journaldev.readfileslinebyline;

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

public class ReadFileLineByLineUsingScanner {

	public static void main(String[] args) {
		try {
			Scanner scanner = new Scanner(new File("sample.txt"));

			while (scanner.hasNextLine()) {
				System.out.println(scanner.nextLine());
			}

			scanner.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}

}

Continue your learning with the Scanner API Doc (Java SE 8).

Reading a File Line-by-Line using Files

java.nio.file.Files is a utility class that contains various useful methods. The readAllLines() method can be used to read all the file lines into a list of strings.

Here is an example program to read a file line-by-line with Files:

ReadFileLineByLineUsingFiles.java
package com.journaldev.readfileslinebyline;

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

public class ReadFileLineByLineUsingFiles {

	public static void main(String[] args) {
		try {
			List<String> allLines = Files.readAllLines(Paths.get("sample.txt"));

			for (String line : allLines) {
				System.out.println(line);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

Continue your learning with the Files API Doc (Java SE 8).

Reading a File Line-by-Line using RandomAccessFile

You can use RandomAccessFile to open a file in read mode and then use its readLine method to read a file line-by-line.

Here is an example program to read a file line-by-line with RandomAccessFile:

ReadFileLineByLineUsingRandomAccessFile.java
package com.journaldev.readfileslinebyline;

import java.io.IOException;
import java.io.RandomAccessFile;

public class ReadFileLineByLineUsingRandomAccessFile {

	public static void main(String[] args) {
		try {
			RandomAccessFile file = new RandomAccessFile("sample.txt", "r");
			String str;

			while ((str = file.readLine()) != null) {
				System.out.println(str);
			}

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

}

Continue your learning with the RandomAccessFile API Doc (Java SE 8).

Conclusion

In this article, you learned about different ways to use Java to read the contents of a file line-by-line.

Continue your learning with more Java tutorials.

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About the authors
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Pankaj

author

Developer and author at DigitalOcean.

Default avatar
Developer and author at DigitalOcean.

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JournalDev
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November 9, 2020

SO what im trying to do is reading each line from a file (named fileName) and writing it into a new file (named fileName2), so basically a copier. How would you do that?

- Ana Pathak

    JournalDev
    DigitalOcean Employee
    DigitalOcean Employee badge
    May 29, 2020

    Is there a way to read a specific line from a file without first reading all previous lines if you know the line length? I’m seeking something analogous to the BASIC code OPEN FILE$ AS 1 LEN = 5 READ #1, 5, LINE% READ #1, LINE%, DESC$

    - Jeff Mullen

      JournalDev
      DigitalOcean Employee
      DigitalOcean Employee badge
      November 12, 2019

      I write a file handling program, I read data from file. In a file a create a table(name,age,clg) when I read data,I get data with column name but I want only data nat file name please suggest me how can do

      - Sp

        JournalDev
        DigitalOcean Employee
        DigitalOcean Employee badge
        April 9, 2019

        Thanks for your tutorials. Is there a way to grab each individual line and assign it to a variable? Somthing like String line [ i } = reader.readLine(); String line1 = line[ o ]; String line2 = line [1 ]; and so on. I tried this and I get the first line on the first line1 string with the rest as nulls. Then i get the first and second line with the rest as nulls on line2 string.

        - Bill Melendez

          JournalDev
          DigitalOcean Employee
          DigitalOcean Employee badge
          February 13, 2019

          I want to create a java program to read input from text file but don’t want to read all the lines at once,Instead I want my Java program to read Input as in when required line by line. need help… Thanks a lot , for giving a shot to my query.

          - Dinesh

            JournalDev
            DigitalOcean Employee
            DigitalOcean Employee badge
            December 17, 2014

            Hello I have to create java program in such a way that output should be print on thermal printer for which paper size ,font size etc should be modified with text file ( template )…I have created program which read normal file and print but how to handle paper size anf font size things pls help me out there

            - Rinku

              JournalDev
              DigitalOcean Employee
              DigitalOcean Employee badge
              February 6, 2013

              Looks very good. Would you be so kind to give an example on how to read random lines from a file?

              - Vulco Viljoen

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