Java File length()

In this guide, you will learn about the File length() method in Java programming and how to use it with an example.

1. File length() Method Overview

Definition:

The length() method of the File class returns the length of the file (in bytes) denoted by the File object. If the file does not exist, or if it's a directory, then this method returns 0.

Syntax:

public long length()

Parameters:

None.

Key Points:

- The method returns a long value representing the size of the file in bytes.

- If the file does not exist or if it's a directory, the method returns 0.

- It can be used to determine if a file is empty (i.e., its length is 0).

- This method doesn't throw exceptions if the file doesn't exist but simply returns 0.

- This method doesn't read the content of the file, so it's relatively efficient for checking the size of large files.

2. File length() Method Example

import java.io.File;

public class FileLengthExample {
    public static void main(String[] args) {
        // Creating a File object
        File file = new File("sample.txt");

        // Getting the length of the file
        long length = file.length();

        // Printing the length
        System.out.println("Length of sample.txt: " + length + " bytes");
    }
}

Output:

Length of sample.txt: 12345 bytes  // Assuming the file has 12345 bytes of data.

Explanation:

In the demonstrated example, a File object, file, representing the "sample.txt" file is created. When invoking the length() method on this object, it returns the size of the file in bytes. This is then printed out to the console. If "sample.txt" didn't exist or was a directory, the printed length would be 0 bytes. 

The length() method is beneficial to quickly gauge the size of a file without having to read its content.