Handling File Exceptions

⚠️ What is a File Exception?

When working with files in Java (like reading, writing, creating), things can go wrong — the file might:

• Not exist ❌

• Be inaccessible 🔒

• Be already created or locked 🔄

• Be in a wrong path 🛣️

Java handles such problems using exceptions — and you must handle them using try-catch blocks.

🧱 Common File-Related Exceptions

1️⃣ Example 1: Handling IOException during file creation

import java.io.File;
import java.io.IOException;

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

        try {
            if (file.createNewFile()) {
                System.out.println("File created: " + file.getName());
            } else {
                System.out.println("File already exists.");
            }
        } catch (IOException e) {
            System.out.println("An error occurred while creating the file.");
            e.printStackTrace(); // Shows the actual error details
        }
    }
}

🧠 Explanation:

• A File object is created to represent a file named example.txt.

• The program tries to create the file using createNewFile().

• If the file is created successfully, a message is printed confirming the creation.

• If the file already exists, a message says so.

• If there's an error (like permission issues or invalid path), an IOException is caught.

• The catch block displays a custom error message and prints the error details using e.printStackTrace()

2️⃣ Example 2: Handling FileNotFoundException during reading

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

public class ReadFile {
    public static void main(String[] args) {
        try {
            File file = new File("data.txt");
            Scanner reader = new Scanner(file);

            while (reader.hasNextLine()) {
                String data = reader.nextLine();
                System.out.println(data);
            }

            reader.close();
        } catch (FileNotFoundException e) {
            System.out.println("File not found. Please check the filename.");
            e.printStackTrace();
        }
    }
}

🧠 Explanation:

• A File object is created to represent data.txt.

• A Scanner is used to read the contents of the file line by line.

• hasNextLine() checks if more lines are present in the file.

• nextLine() reads and stores each line as a String.

• Each line is printed to the console.

• After reading, the Scanner is closed using reader.close().

• If the file does not exist, a FileNotFoundException is caught.

• The catch block prints a friendly message and the actual error details using e.printStackTrace().

3️⃣ Example 3: Catching multiple exceptions

try {
    // File operations
} catch (FileNotFoundException e) {
    System.out.println("File not found.");
} catch (IOException e) {
    System.out.println("Input/output error.");
}

🧠 Explanation:

• The try block contains file-related operations (like reading, writing, creating).

• If the file is not found, FileNotFoundException is caught, and a message is shown.

• If a general input/output error occurs (e.g., can't read/write), IOException is caught.

• Each catch block handles a specific type of error, so your program doesn't crash.

• This is an example of multi-catch to handle different possible exceptions separately.

🔐 Tip: Always close your file resources

Use .close() for Scanner, FileWriter, etc. Or use try-with-resources for auto-close:

try (Scanner reader = new Scanner(new File("data.txt"))) {
    // Read file
} catch (FileNotFoundException e) {
    // Handle error
}

📝 Summary