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)
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How do you read from a file in Java?
Using a Scanner
Using a PrintWriter
Using a FileWriter
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What is the purpose of PrintWriter in file handling?
To read from a file
To close a file
To write to a file
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How can you copy a file in Java?
Using FileWriter
Using Scanner
Using Files.copy()
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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
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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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