How to Download File in Java

1. Download a File Using the java.nio Package in Java
2. Download a File Using FileUtils.copyURLToFile() in Java
3. Download a File Using Files.copy() in Java

This article teaches us how we can download a file in Java using various methods. Below, we will see four ways to download a file in Java. Our main focus is only to download a file from an URL that we will use in the examples.

Download a File Using the java.nio Package in Java

The first example in this tutorial uses the java.nio package that is just an improved and advanced alternative to Java’s traditional java.io. The nio part stands for New Input/Output, which says that it has better capabilities than the former package. java.nio provides new networking methods that we can use.

In the following code, first, we create a URL object fetchWebsite with the URL from where we want to download our file. Next, we construct a channel that reads the stream from fetchWebsite, and we do that by calling the newChannel() method of the Channels class. To create a stream we call openStream() from fetchWebsite.

Now, we create a FileOutputStream object fos that creates a file locally with the name specified. Finally, we get the file from the online source using the transferFrom() method. This method transfers the data from source to a FileChannel that writes into the fos. transferFrom() takes three arguments, first is the readableByteChannel object, second is the position from where we want to start writing the file, i.e., 0th position and lastly the maximum number of bytes to transfer.

import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

public class DownloadFile {
  public static void main(String[] args) throws IOException {
    URL fetchWebsite = new URL(
        "https://theswissbay.ch/pdf/Gentoomen%20Library/Programming/Java/Introduction%20to%20Java%20IO.pdf");
    ReadableByteChannel readableByteChannel = Channels.newChannel(fetchWebsite.openStream());

    try (FileOutputStream fos = new FileOutputStream("C:\\Users\\Downloads\\IntroToJava.pdf")) {
      fos.getChannel().transferFrom(readableByteChannel, 0, Long.MAX_VALUE);
    }
  }
}

Download a File Using FileUtils.copyURLToFile() in Java

The next best way to download a file from an online source is to use the FileUtils.copyUrlToFile() method included in the Apache Commons-IO library.

We use the following code to include the dependency in the project.

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-io</artifactId>
    <version>1.3.2</version>
</dependency>

Below, we create a URL object with the link to the online file resource. Next, we create a local file where the downloaded file can reside. To do this, we make an object of the File class and pass the file’s name with the extension into its constructor.

At last, we call the copyURLToFile() method from the FileUtils class that takes two arguments: the URL object and the file object.

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

public class DownloadFile {
  public static void main(String[] args) throws IOException {
    URL fetchWebsite = new URL(
        "https://theswissbay.ch/pdf/Gentoomen%20Library/Programming/Java/Introduction%20to%20Java%20IO.pdf");

    File file = new File("JavaIo.pdf");

    FileUtils.copyURLToFile(fetchWebsite, file);
  }
}

Download a File Using Files.copy() in Java

Just like the first example, we use the java.nio package but to call a different method. copy() is a method of the Files class. As the function’s name suggests, it copies a file to the specified target.

In the code, we have a URL object fetchWebsite that points to the source of the file. We create an object of Path that tells the target where we want the file to be copied. Next, we open a stream to get the bytes from the online resource and pass the inputSteam to copy(). As it takes three arguments, the first and second are the inputStream and path objects, while the third specifies the CopyOption or the way the copy operation should be performed. We use StandardCopyOption.REPLACE_EXISTING to replace the file if it already exists.

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;

public class DownloadFile {
  public static void main(String[] args) throws IOException {
    URL fetchWebsite = new URL(
        "https://theswissbay.ch/pdf/Gentoomen%20Library/Programming/Java/Introduction%20to%20Java%20IO.pdf");

    Path path = Paths.get("JavaIO.pdf");
    try (InputStream inputStream = fetchWebsite.openStream()) {
      Files.copy(inputStream, path, StandardCopyOption.REPLACE_EXISTING);
    }
  }
}