How to read file line by line in Java

by Online Tutorials Library July 22, 2022

How to read file line by line in Java

There are following ways to read a file line by line.

BufferedReader Class
Scanner class

Using BufferedReader Class

Using the Java BufferedRedaer class is the most common and simple way to read a file line by line in Java. It belongs to java.io package. Java BufferedReader class provides readLine() method to read a file line by line. The signature of the method is:

The method reads a line of text. It returns a string containing the contents of the line. The line must be terminated by any one of a line feed (“n”) or carriage return (“r”).

Example of read a file line by line using BufferedReader class

In the following example, Demo.txt is read by FileReader class. The readLine() method of BufferedReader class reads file line by line, and each line appended to StringBuffer, followed by a linefeed. The content of the StringBuffer are then output to the console.

  import java.io.*;  public class ReadLineByLineExample1  {  public static void main(String args[])  {  try  {  File file=new File(“Demo.txt”);    //creates a new file instance  FileReader fr=new FileReader(file);   //reads the file  BufferedReader br=new BufferedReader(fr);  //creates a buffering character input stream  StringBuffer sb=new StringBuffer();    //constructs a string buffer with no characters  String line;  while((line=br.readLine())!=null)  {  sb.append(line);      //appends line to string buffer  sb.append(“n”);     //line feed   }  fr.close();    //closes the stream and release the resources  System.out.println(“Contents of File: “);  System.out.println(sb.toString());   //returns a string that textually represents the object  }  catch(IOException e)  {  e.printStackTrace();  }  }  }  

Output:

How to read file line by line in Java

Using the Scanner class

Java Scanner class provides more utility methods compare to BufferedReader class. Java Scanner class provides the nextLine() method to facilitates line by line of file’s content. The nextLine() methods returns the same String as readLine() method. The Scanner class can also read a file form InputStream.

Example of read a file line by line using Scanner class

  import java.io.*;  import java.util.Scanner;  public class ReadLineByLineExample2  {  public static void main(String args[])  {  try  {  //the file to be opened for reading  FileInputStream fis=new FileInputStream(“Demo.txt”);   Scanner sc=new Scanner(fis);//file to be scanned  //returns true if there is another line to read  while(sc.hasNextLine())  {  System.out.println(sc.nextLine());//returns the line that was skipped  }  sc.close();//closes the scanner  }  catch(IOException e)  {  e.printStackTrace();  }  }  }  

Output:

How to read file line by line in Java

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How to read file line by line in Java

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