Download file from URL android programmatically

Today we will learn how to download a file from URL in java. We can use java.net.URL openStream() method to download file from URL in java program. We can use Java NIO Channels or Java IO InputStream to read data from the URL open stream and then save it to file.

Java Download File from URL

package com.journaldev.files;

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

public class JavaDownloadFileFromURL {

    public static void main(String[] args) {
        String url = "https://www.journaldev.com/sitemap.xml";
        
        try {
            downloadUsingNIO(url, "/Users/pankaj/sitemap.xml");
            
            downloadUsingStream(url, "/Users/pankaj/sitemap_stream.xml");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void downloadUsingStream(String urlStr, String file) throws IOException{
        URL url = new URL(urlStr);
        BufferedInputStream bis = new BufferedInputStream(url.openStream());
        FileOutputStream fis = new FileOutputStream(file);
        byte[] buffer = new byte[1024];
        int count=0;
        while((count = bis.read(buffer,0,1024)) != -1)
        {
            fis.write(buffer, 0, count);
        }
        fis.close();
        bis.close();
    }

    private static void downloadUsingNIO(String urlStr, String file) throws IOException {
        URL url = new URL(urlStr);
        ReadableByteChannel rbc = Channels.newChannel(url.openStream());
        FileOutputStream fos = new FileOutputStream(file);
        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
        fos.close();
        rbc.close();
    }

}

downloadUsingStream: In this method of java download file from URL, we are using URL openStream method to create the input stream. Then we are using a file output stream to read data from the input stream and write to the file. downloadUsingNIO: In this download file from URL method, we are creating byte channel from URL stream data. Then use the file output stream to write it to file. You can use any of these methods to download the file from URL in java program. If you are looking for performance, then do some analysis by using both methods and see what suits your need.

You can checkout more Java IO examples from our GitHub Repository.

This post will discuss how to download a file from a remote URL in Kotlin.

1. Using FileChannel.transferFrom() function

The FileChannel#transferFrom() function is used to transfer bytes into this channel’s file from a readable byte channel. It accepts three parameters – the source channel, the position within the file to begin the transfer, and the maximum number of bytes to be transferred.

Its usage is demonstrated below using the use() function, which takes care of closing the opened streams and channels.

Download Code

2. Using Files.copy() function

We can also use the Files.copy() function to copy all bytes from an input stream to a file. It takes the input stream to read from and the path to the file and optional params indicating how copying should be done.

Download Code

3. Using BufferedInputStream

Finally, we can read the file from the input stream byte-by-byte and write the bytes to a file output stream. This would translate to a simple code below:

Download Code

That’s all about downloading a file from a remote URL in Kotlin.

Thanks for reading.

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