Reading and Writing Files in Java

Introduction

Reading and writing files is a common task in Java programming. Java provides several classes for handling file I/O operations, such as FileInputStream, FileOutputStream, BufferedReader, BufferedWriter, FileReader, and FileWriter. This guide covers basic file reading and writing operations using these classes.

1. Reading Files

Reading Text Files

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadTextFileExample {
    public static void main(String[] args) {
        try (BufferedReader reader = new BufferedReader(new FileReader("example.txt"))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            System.out.println("An error occurred: " + e.getMessage());
        }
    }
}

Reading Binary Files

import java.io.FileInputStream;
import java.io.IOException;

public class ReadBinaryFileExample {
    public static void main(String[] args) {
        try (FileInputStream fis = new FileInputStream("example.bin")) {
            int byteData;
            while ((byteData = fis.read()) != -1) {
                System.out.print((char) byteData);
            }
        } catch (IOException e) {
            System.out.println("An error occurred: " + e.getMessage());
        }
    }
}

2. Writing Files

Writing Text Files

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class WriteTextFileExample {
    public static void main(String[] args) {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter("example.txt"))) {
            writer.write("Hello, World!");
            writer.newLine();
            writer.write("This is a new line.");
        } catch (IOException e) {
            System.out.println("An error occurred: " + e.getMessage());
        }
    }
}

Writing Binary Files

import java.io.FileOutputStream;
import java.io.IOException;

public class WriteBinaryFileExample {
    public static void main(String[] args) {
        try (FileOutputStream fos = new FileOutputStream("example.bin")) {
            byte[] data = { 72, 101, 108, 108, 111, 44, 32, 87, 111, 114, 108, 100, 33 };
            fos.write(data);
        } catch (IOException e) {
            System.out.println("An error occurred: " + e.getMessage());
        }
    }
}

Conclusion

Reading and writing files in Java is straightforward using the classes provided in the java.io package. Whether you need to handle text files or binary files, Java provides the necessary tools to perform file I/O operations efficiently. By understanding and using these classes effectively, you can manipulate files in your Java applications with ease.