File Handling in Java (IO) – Complete Tutorial

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Last Updated on: 26th Nov 2025 13:05:40 PM

File Handling is one of the most important concepts in Java, especially for real-world applications where data needs to be stored permanently.
Java provides a powerful IO (Input/Output) package in java.io  and java.nio.file for performing operations such as:

• Creating files

• Reading files

• Writing files

• Appending data

• Deleting files

• Handling directories

Java File Handling is widely used in real-life applications like:

• Saving logs

• Storing user data

• Exporting reports

• Uploading files

• Reading configuration files

• Processing large datasets

 

In Java, File Handling refers to reading and writing data to/from files on the disk.
Java uses Streams to perform file operations. 

 

A Stream is a flow of data — either input (read) or output (write).

 

Java IO Has 2 Major Types of Streams:

Stream Type	Description	Example Classes
Byte Streams	Reads/Writes data in bytes (binary files)	FileInputStream, FileOutputStream
Character Streams	Reads/Writes data in characters (text files)	FileReader, FileWriter

 

Also, Java File Handling includes classes such as:

• File

• FileReader

• FileWriter

• BufferedReader

• BufferedWriter

• FileInputStream

• FileOutputStream

• PrintWriter

• Scanner

• Files (NIO)

• Paths (NIO)

 

Why File Handling Is Important?

Most real-world applications need to store information permanently:

• A banking system stores transaction logs

• A school ERP stores student data

• Android apps use internal file storage

• Servers store access and error logs

• Websites store uploaded files

 

Without File Handling, all data would be lost after program execution.

So Java provides a robust and secure IO system to work with files.

 

Key Operations in Java File Handling

Java allows:

1. Create a file

2. Write data to file

3. Read data from file

4. Append data

5. Delete a file

6. Create folders (directories)

7. Read all files inside a folder

Below, each topic is explained in detail.

 

1. The File Class – Creation, Checking, Deleting Files

java.io.File is used to represent files and directories.

Create File Example

import java.io.*;

public class CreateFile {
    public static void main(String[] args) {
        try {
            File f = new File("test.txt");
            if (f.createNewFile()) {
                System.out.println("File created: " + f.getName());
            } else {
                System.out.println("File already exists");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

Output:

File created: test.txt

 

2. Writing to a File using FileWriter

import java.io.*;

public class WriteFile {
    public static void main(String[] args) {
        try {
            FileWriter fw = new FileWriter("data.txt");
            fw.write("Welcome to iKeySkills File Handling Tutorial.");
            fw.close();
            System.out.println("Data written successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

Output:

Data written successfully.

 

3. Reading From a File using FileReader

import java.io.*;

public class ReadFile {
    public static void main(String[] args) {
        try {
            FileReader fr = new FileReader("data.txt");
            int ch;
            while ((ch = fr.read()) != -1) {
                System.out.print((char) ch);
            }
            fr.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

Output:

Welcome to iKeySkills File Handling Tutorial.

 

4. Appending Data to File

import java.io.*;

public class AppendFile {
    public static void main(String[] args) {
        try {
            FileWriter fw = new FileWriter("data.txt", true);
            fw.write("\nThis line is appended.");
            fw.close();
            System.out.println("Data appended successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

Output:

Data appended successfully.

 

5. Using BufferedWriter & BufferedReader (Fast IO)

BufferedWriter Example:

import java.io.*;

public class BufferedWrite {
    public static void main(String[] args) {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter("notes.txt"));
            bw.write("BufferedWriter writes fast!");
            bw.close();
            System.out.println("Data written.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

BufferedReader Example:

import java.io.*;

public class BufferedRead {
    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new FileReader("notes.txt"));
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
            br.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

6. Using FileInputStream & FileOutputStream (Binary Files)

Used for images, PDFs, audio, videos.

Example:

import java.io.*;

public class BinaryCopy {
    public static void main(String[] args) {
        try {
            FileInputStream fin = new FileInputStream("image.jpg");
            FileOutputStream fout = new FileOutputStream("copy.jpg");

            int b;
            while ((b = fin.read()) != -1) {
                fout.write(b);
            }

            fin.close();
            fout.close();
            System.out.println("Image copied successfully!");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 

7. Reading a File Using Scanner

import java.io.*;
import java.util.*;

public class ScannerRead {
    public static void main(String[] args) throws Exception {
        File f = new File("data.txt");
        Scanner sc = new Scanner(f);

        while (sc.hasNextLine()) {
            System.out.println(sc.nextLine());
        }
        sc.close();
    }
}

 

8. Listing Files in a Folder

import java.io.*;

public class ListFiles {
    public static void main(String[] args) {
        File folder = new File("C:/JavaProjects");

        String[] files = folder.list();
        for (String f : files) {
            System.out.println(f);
        }
    }
}

 

9. Delete a File

import java.io.*;

public class DeleteFile {
    public static void main(String[] args) {
        File f = new File("test.txt");
        if (f.delete()) {
            System.out.println("File deleted.");
        } else {
            System.out.println("Unable to delete.");
        }
    }
}

 

10. Java NIO (Modern File Handling)

java.nio.file provides faster, more powerful file operations.

Example:

import java.nio.file.*;

public class NIOExample {
    public static void main(String[] args) throws Exception {
        Path p = Paths.get("niofile.txt");

        Files.write(p, "NIO writing example".getBytes());

        String content = Files.readString(p);
        System.out.println(content);
    }
}

 

Real-Life Application Example (Log File System)

import java.io.*;
import java.time.*;

public class Logger {
    static void log(String message) throws Exception {
        BufferedWriter bw = new BufferedWriter(new FileWriter("log.txt", true));
        bw.write(LocalDateTime.now() + " : " + message);
        bw.newLine();
        bw.close();
    }

    public static void main(String[] args) throws Exception {
        log("User logged in");
        log("User purchased a course");
    }
}

 

Summary

• Java File Handling allows reading/writing files on disk

• File → create/delete files

• FileWriter, FileReader → text files

• BufferedReader, BufferedWriter → fast processing

• FileInputStream, FileOutputStream → binary files

• Scanner → simple file reading

• Files + Paths (NIO) → modern and powerful

 

Keep practicing — you're doing amazing!

Happy Coding!    

 

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