File Handling in Java

File handling

Examples

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.util.Scanner;

public class FileHandlingExamples {
    public static void main(String[] args) {
        // Example 1: Reading from a file
        // Place the input.txt file in the same directory as your Java source file
        File inputFile = new File("input.txt");
        try {
            Scanner scanner = new Scanner(inputFile);
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                System.out.println(line);
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        // Example 2: Writing to a file
        // The output.txt file will be created in the same directory as your Java source file
        File outputFile = new File("output.txt");
        try {
            PrintWriter writer = new PrintWriter(outputFile);
            writer.println("Hello, world!");
            writer.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        // Example 3: Copying a file
        // Place the source.txt file in the same directory as your Java source file
        File sourceFile = new File("source.txt");
        // The destination.txt file will be created in the same directory as your Java source file
        File destFile = new File("destination.txt");
        try {
            Files.copy(sourceFile.toPath(), destFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

FAQ (interview questions and answers)

1. How do you read from a file in Java?
   Using a Scanner
   Using a PrintWriter
   Using a FileWriter
   
2. What is the purpose of PrintWriter in file handling?
   To read from a file
   To close a file
   To write to a file
   
3. How can you copy a file in Java?
   Using FileWriter
   Using Scanner
   Using Files.copy()
   
4. What is the purpose of the close() method in file handling?
   To open a file
   To close an open file
   To write to a file
   
5. What happens if you attempt to read from a non-existent file?
   An IOException is thrown
   A FileNotFoundException is thrown
   A NoSuchFileException is thrown
   

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