How to read file line by line in Java - BufferedReader Scanner Example Tutorial

Line by Line reading in Java using BufferedReader and Scanner

There are multiple ways to read files line by line in Java. A most simple example of reading file line by line is using BufferedReader which provides the method readLine() for reading files. Apart from generics, enum and varargs Java 1.5  has also introduced several new classes in Java API one of the utility classes is Scanner, which can also be used to read any file line by line in Java. Though BufferedReader is available in Java from JDK 1.1,  java.util.Scanner provides more utility methods compared to BufferedReader. Scanner has method like hasNextLine() and nextLine() to facilitate line by line reading of file's contents.

The nextLine() returns String similar to readLine() but the scanner has more utility methods like nextInt(), nextLong() which can be used to directly read numbers from a file instead of converting String to Integer or other Number classes.

By the way, a Scanner is rather a new approach for reading a file, and BufferedReader is the standard one. This is my 6^th tutorial on Java IO,  In the last couple of post, we have seen creating file and directory in Java, parsing XML files using DOM and how to read properties file in Java. In this post, we will focus on reading the file line by line in Java using both BufferedReader and Scanner.

Reading file line by line in Java - BufferedReader Example

In this example, we are using BufferedReader for reading file content line by line. BufferedReader needs an InputStream which is a FileInputStream in this case and readLine() returns a value of line or null if the end of Stream has reached. The line is terminated with line terminator e.g. \n or \r

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * BufferedReader and Scanner can be used to read line by line from any File or

 * console in Java.
 * This Java program demonstrate line by line reading using BufferedReader in Java

 *

 * @author Javin Paul
 */
public class BufferedReaderExample {  

    public static void main(String args[]) {
     
        //reading file line by line in Java using BufferedReader      
        FileInputStream fis = null;
        BufferedReader reader = null;
     
        try {
            fis = new FileInputStream("C:/sample.txt");
            reader = new BufferedReader(new InputStreamReader(fis));
         
            System.out.println("Reading File line by line using BufferedReader");
         
            String line = reader.readLine();
            while(line != null){
                System.out.println(line);
                line = reader.readLine();
            }          
         
        } catch (FileNotFoundException ex) {
            Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);
         
        } finally {
            try {
                reader.close();
                fis.close();
            } catch (IOException ex) {
                Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
  }

Output:
Reading File line by line using BufferedReader
first line in file
second line
third line
fourth line
fifth line
last line in file

while using FileInputStream or any IO Reader don't forget to close the stream in finally block so that file descriptor associated with this operation get released. If not closed properly Java program may leak file descriptors which is a limited resource and in worst case program will not be able to open any new file. If you are Java 7 then you can use Automatic resource management or ARM blocks to let those resource automatically get closed by Java.

Reading file line by line in Java - Scanner Example

Scanner is new addition in Java 1.5 along with several other changes like auto-boxing and has been a preferred choice for reading inputs from the console. Since Scanner is able to read from InputStream , it can also be used to read from text File and it provide many utility methods to read line by line contents using nextLine() or nextInt() etc.

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

/**
 * @author Javin Paul

 * Java program to read file line by line using Scanner. Scanner is a rather new

 * utility class in Java and introduced in JDK 1.5 and preferred way to read input

 * from console.
 */
public class ScannerExample {
 

    public static void main(String args[]) throws FileNotFoundException  {
     
       //Scanner Example - read file line by line in Java using Scanner
        FileInputStream fis = new FileInputStream("C:/sample.txt");
        Scanner scanner = new Scanner(fis);
     
        //reading file line by line using Scanner in Java
        System.out.println("Reading file line by line in Java using Scanner");
     
        while(scanner.hasNextLine()){
            System.out.println(scanner.nextLine());
        }
     
        scanner.close();
    }  
     
}

Output:
Reading file line by line in Java using Scanner
first line in file
second line
third line
fourth line
fifth line
last line in file

That's all on How to read files line by line in Java. We have seen two simple examples of line-by-line reading using BufferedReader and Scanner. If you look code with Scanner looks cleaner and give a wide variety of data conversion method it supports, it just a handy choice for reading file line by line in Java.

Other Java IO tutorials from the Javarevisited blog

Quick guide of Memory Mapped IO in Java

How to read XML documents using SAX parser

Difference between DOM and SAX parser in Java

JDK 7 multi-catch block for Exception

JDK 7 String in Switch feature - Overview