Java Program to Read a Large Text File Line by Line - GeeksforGeeks

13 Sep, 2021
As we are are well verse with this topic let us put more stress in order to figure out minute differences between them. Here we are supposed to read from a file on the local directory where a text file is present say it be ‘gfg.txt’. Let the content inside the file be as shown below:
Geeks for Geeks.
A computer science portal.
Welcome to this portal.
Hello Geek !!!
Note: Keep a check that prior doing anything first create a file on the system repository to deal with our program\writing a program as we will be accessing the same directory through our programs.
Methods:
Using Scanner classUsing BufferedReaader class
Using Scanner class
Using BufferedReaader class
Method 1: Using Scanner class
Scanner is a class in java.util package used for obtaining the input of the primitive types like int, double, etc. and strings. It is the easiest way to read input in a Java program, though not very efficient if you want an input method for scenarios where time is a constraint like in competitive programming. Scanner class is used to read the large file line by line. A Scanner breaks its input into tokens, which  by default matches the whitespace. 
Example
Java
// Java Program to Read a Large Text File Line by Line// Using Scanner class // Importing required classesimport java.io.*;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.InputStream;import java.nio.charset.StandardCharsets;import java.util.Scanner; // Main classpublic class GFG {     // Main driver method    public static void main(String[] args)        throws FileNotFoundException    {         // Declaring and initializing the string with        // custom path of a file        String path = "C:\\Users\\HP\\Desktop\\gfg.txt";         // Creating an instance of Inputstream        InputStream is = new FileInputStream(path);         // Try block to check for exceptions        try (Scanner sc = new Scanner(                 is, StandardCharsets.UTF_8.name())) {             // It holds true till there is single element            // left in the object with usage of hasNext()            // method            while (sc.hasNextLine()) {                 // Printing the content of file                System.out.println(sc.nextLine());            }        }    }}
Output: 
Geeks for Geeks.
A computer science portal.
Welcome to this portal.
Hello Geek !!!
Method 2: Using BufferedReader class
BufferedReader is used to read the file line by line. Basically, BufferedReader() is used for the processing of large files. BufferedReader is very efficient for reading. 
Note: Specify the size of the BufferReader or keep that size as a Default size of BufferReader. The default size of BufferReader is 8KB. 
Syntax:
BufferedReader in = new BufferedReader(Reader in, int size);
Example:
Java
// Java Program to Read a Large Text File Line by Line// Using BufferedReader class // Importing required classesimport java.io.*;import java.io.BufferedReader;import java.io.FileReader;import java.io.IOException; // Main classpublic class GFG {     // Main driver method    public static void main(String[] args)    {         // Declaring a string and initializing it with        // path of file present on the system        String path = "C:\\Users\\HP\\Desktop\\gfg.txt";         // Try block to check for exceptions        try (BufferedReader br             = new BufferedReader(new FileReader(path))) {             // Declaring a new string            String str;             // It holds true till threre is content in file            while ((str = br.readLine()) != null) {                 // Printing the file data                System.out.println(br);            }        }         // Catch block to handle the exceptions        catch (IOException e) {             // Display pop up message if exceptionn occurs            System.out.println(                "Error while reading a file.");        }    }}
Output: 
Geeks for Geeks.
A computer science portal.
Welcome to this portal.
Hello Geek !!!
anikakapoor
sweetyty
Java-Files
Picked
Java
Java Programs
Java
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Stream In Java
Constructors in Java
Different ways of Reading a text file in Java
Exceptions in Java
Functional Interfaces in Java
Convert a String to Character array in Java
Java Programming Examples
Convert Double to Integer in Java
Implementing a Linked List in Java using Class
How to Iterate HashMap in Java?