Java Program: File reading and empty file exception handling

Last update on December 21 2024 09:39:22 (UTC/GMT +8 hours)

Write a Java program that reads a file and throws an exception if the file is empty.

Sample Solution:

Java Code:

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

public class Empty_File_Check {
  public static void main(String[] args) {
    try {
      checkFileNotEmpty("test1.txt");
      System.out.println("File is not empty.");
    } catch (FileNotFoundException e) {
      System.out.println("Error: " + e.getMessage());
    } catch (EmptyFileException e) {
      System.out.println("Error: " + e.getMessage());
    }
  }

  public static void checkFileNotEmpty(String fileName) throws FileNotFoundException, EmptyFileException {
    File file = new File(fileName);
    Scanner scanner = new Scanner(file);

    if (!scanner.hasNextLine()) {
      scanner.close();
      throw new EmptyFileException("File is empty.");
    }

    scanner.close();
  }
}

class EmptyFileException extends Exception {
  public EmptyFileException(String message) {
    super(message);
  }
}

Sample Output:

Content of the file (test1.txt):
0
0
0

File is not empty.

Content of the file (test1.txt):
 
Error: File is empty.

Explanation:

In the above exercise,

• The program includes two classes: Empty_File_Check and EmptyFileException.
• The Empty_File_Check class contains the main method, which serves as the program's entry point.
• In the main method, we call the checkFileNotEmpty method, passing the file name "test1.txt" as an argument. We handle two types of exceptions: FileNotFoundException and EmptyFileException.
• The checkFileNotEmpty method checks if a file is empty. It takes the file name as a parameter and can potentially throw two types of exceptions: FileNotFoundException and EmptyFileException.
• Inside the checkFileNotEmpty method, we create a File object using the provided file name. We also create a Scanner object to read the file's contents.
• We use an if statement to check if the scanner does not have a next line, indicating that the file is blank. If the file is empty, we throw an EmptyFileException with the message "File is empty."
• After checking the file, we close the Scanner object.
• The EmptyFileException class is a custom exception class that extends the base Exception class. It provides a constructor that takes a message parameter and passes it to the superclass constructor using the super keyword.
• If a FileNotFoundException occurs in the main method, it is caught, and an appropriate error message is printed.
• If an EmptyFileException occurs in the checkFileNotEmpty method, it is caught in the main method. The error message indicating an empty file is printed.

Flowchart:

Java Code Editor:

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