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:

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:

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:

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:

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.