Java Program: File reading and empty file exception handling

Last update on May 23 2025 13:09:33 (UTC/GMT +8 hours)

5. Throw Exception if File is Empty

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:

Flowchart: Java Exception Exercises - File reading and empty file exception handling.'

For more Practice: Solve these Related Problems:

Write a Java program to read a file and throw a custom EmptyFileException if its content is empty.
Write a Java program to check the file size using NIO and throw an exception if the file is zero bytes.
Write a Java program to read a file and throw an exception if it contains only whitespace characters.
Write a Java program to validate a file's content before processing and throw an exception if no valid data is found.

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