`Files.size`

What is the size in bytes of a file? In Java this can be determined with the Files class, but we first need to create a Path.

To create a path, we can use the getPath() method with any number of String arguments. Then we can invoke the Files.size method with this path.

Example

This program gets the file size of a file in the programs directory with the name example.txt. When you run this program, be sure to change the path to one that exists.

Step 1 We get a Path instance. We need a FileSystem to get a path, so we get the default with FileSystems getDefault().

Step 2 We use a try-catch block and pass the path we created to the Files.size method.

Step 3 If the file did not exist, an IOException will be encountered. In this situation we just set the size to 0.

Step 4 We print the size of the file. On the test system, the example.txt file as reported by macOS was 20 bytes.

import java.io.*;
import java.nio.file.*;

public class Program {
    public static void main(String[] args) {

        // Step 1: get the default file system, and get a path in the programs directory.
        var path = FileSystems.getDefault().getPath("programs", "example.txt");

        // Step 2: pass the path to the Files.size method.
        long size;
        try {
            size = Files.size(path);
        } catch (IOException ex) {
            // Step 3: if an IOException occurred, just use the size 0.
            size = 0;
        }

        // Step 4: print the size of the file.
        System.out.println(size);
    }
}
20

To get the size of a file in Java, we invoke the Files.size method. If you haven't used this method before (or recently), creating the required Path can be a challenge.