Java file size

last modified January 27, 2024

In this article we show several ways how to determine the size of a file in Java.

File size is a measure of how much data a computer file contains or, alternately, how much storage it consumes. The file size is usually expressed in bytes.

In Java, we can determine the size of a file with File, FileChannel, Files, and Apache Commons' FileUtils. A a rule of thumb, in new code we should use the Files class.

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In our examples, we are going to use the words.txt file located in src/main/resources directory.

Java file size with File

The length method of File returns the file size. This is the oldest API to find out the size of a file in Java.

package com.zetcode;

import java.io.File;

public class JavaFileSizeEx {
    
    public static void main(String[] args) {
        
        String fileName = "src/main/resources/words.txt";
        
        File f = new File(fileName);
        long fileSize = f.length();
        
        System.out.format("The size of the file: %d bytes", fileSize);
    }
}

The code example determines the file size using File's length method.

Java file size with FileChannel

FileChannel has the size method to determine the size of the file.

package com.zetcode;

import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;

public class JavaFileSizeEx2 {

    public static void main(String[] args) throws IOException {

        String fileName = "src/main/resources/words.txt";

        Path filePath = Paths.get(fileName);

        FileChannel fileChannel = FileChannel.open(filePath);
        long fileSize = fileChannel.size();
        
        System.out.format("The size of the file: %d bytes", fileSize);
    }
}

The code example determines the file size using FileChannel's size method.

Java file size with Files

Files has the size method to determine the size of the file. This is the most recent API and it is recommended for new Java applications.

package com.zetcode;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class JavaFileSizeEx3 {

    public static void main(String[] args) throws IOException {

        String fileName = "src/main/resources/words.txt";

        Path filePath = Paths.get(fileName);
        long fileSize = Files.size(filePath);        

        System.out.format("The size of the file: %d bytes", fileSize);
    }
}

The code example determines the file size using Files' size method.

Java file size with FileUtils

In the last example, we determine the file size with Apache Commons' FileUtils. Its method for finding out the file size is sizeOf.

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>

For this example, we need the commons-io dependency.

package com.zetcode;

import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;

public class JavaFileSizeEx4 {

    public static void main(String[] args) throws IOException {

        String fileName = "src/main/resources/words.txt";
        File f = new File(fileName);

        long fileSize = FileUtils.sizeOf(f);        

        System.out.format("The size of the file: %d bytes", fileSize);
    }
}

The code example determines the file size using Apache Commons' FileUtils' sizeOf method.

Source

Java Basic I/O - tutorial

In this article we have shown how to determine the size of a file in Java.

Author

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

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