Reading from a File

🔰 Introduction

File Handling in Java lets you read/write files on disk. You can:

• Read line by line using BufferedReader or Scanner

• Parse data using Scanner’s methods (nextLine(), nextInt(), etc.)

📘 Method 1: Reading a File using FileReader and BufferedReader

❔ What is FileReader?

• FileReader is a class in Java used to read character files.

• It reads the file character by character, making it suitable for text files.

• But it's not efficient for large files since it reads one character at a time.

❔ What is BufferedReader?

• BufferedReader is a wrapper over FileReader that buffers the input for faster reading.

• It allows us to read the file line by line using .readLine(), which is much faster than reading character by character.

✅ Why use both together?

Using them together:

BufferedReader br = new BufferedReader(new FileReader("file.txt"));

• FileReader handles reading from the file.

• BufferedReader improves performance and provides useful methods like .readLine().

🧾 Java Program to Read a File

import java.io.*;

public class ReadFileExample {
    public static void main(String[] args) {
        try {
            FileReader fr = new FileReader("example.txt");
            BufferedReader br = new BufferedReader(fr);

            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }

            br.close();
            fr.close();
        } catch (IOException e) {
            System.out.println("File not found or error reading the file.");
            e.printStackTrace();
        }
    }
}

📄 Sample File: example.txt

Java is simple.
It is platform independent.
File handling is important.

Java is simple.
It is platform independent.
File handling is important.

🧾 Explanation of Code

🔐 When to Use This Method?

📘 Method 2: Reading a File using Scanner

📦 What is Scanner?

The Scanner class (from the java.util package) is used to read input easily — from the console, files, or strings.

It parses primitive types like int, double, and also String, making it very versatile for both console input and file reading.

✅ Import Statement

Before using Scanner, you must import it:

import java.util.Scanner;

📘 Use Case 1: Reading Input from Console

import java.util.Scanner;

public class ConsoleInputExample {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter your name: ");
        String name = sc.nextLine();

        System.out.print("Enter your age: ");
        int age = sc.nextInt();

        System.out.println("Hello " + name + ", you are " + age + " years old.");

        sc.close();
    }
}

🧪 Sample Input:

Enter your name: Alex
Enter your age: 22

Hello Alex, you are 22 years old.

📘 Use Case 2: Reading Input from a File using Scanner

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

public class FileScannerExample {
    public static void main(String[] args) {
        try {
            File file = new File("example.txt");
            Scanner sc = new Scanner(file);

            while (sc.hasNextLine()) {
                String line = sc.nextLine();
                System.out.println(line);
            }

            sc.close();
        } catch (FileNotFoundException e) {
            System.out.println("File not found.");
            e.printStackTrace();
        }
    }
}

📄 Sample File: example.txt

Java is simple.
It is platform independent.
File handling is important.

Java is simple.
It is platform independent.
File handling is important.

🔧 Common Scanner Methods

⚠️ Important Tips

1. After reading a number using nextInt() or nextDouble(), use nextLine() to clear the leftover newline:

   int age = sc.nextInt();
   sc.nextLine();  // Clear newline

2. Always close the scanner after use to free resources:

   sc.close();

📌 When to Use Scanner?