Multithreaded File Downloader A Java application that downloads files from the internet using multiple threads in parallel to improve download speed. Overview This application allows you to download files from URLs by splitting the download into multiple parts and downloading them concurrently using separate threads. After all parts are downloaded, they are merged back into a single file. Features
Download files using multiple threads in parallel Automatically determine file size and divide the work among threads Display download progress for each thread Merge file parts into the final file Supports HTTP/HTTPS downloads Handles redirects and standard HTTP responses
Requirements
Java 8 or higher Internet connection
Usage Compilation bashjavac MultiThreadedDownloader.java Running the Program bashjava MultiThreadedDownloader Where:
is the URL of the file you want to download is the local path where you want to save the file is the number of concurrent download threads to use
Example git bash java MultiThreadedDownloader https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Snake_River_%285mb%29.jpg/2560px-Snake_River_%285mb%29.jpg snake_river.jpg 4
This will download the Snake River image from Wikimedia Commons using 4 threads and save it as "snake_river.jpg". How It Works
File Size Determination
The program first sends a request to determine the total file size
Chunking
The file is divided into equal-sized chunks based on the number of threads
Parallel Download
Each thread downloads its assigned chunk using HTTP Range requests Each chunk is saved to a temporary file
Progress Tracking
Download progress is displayed for each thread
Merging
After all threads complete, the temporary files are merged into the final file
Cleanup
Temporary files are deleted after successful download
Troubleshooting 404 Error (Not Found)
Verify that the URL is correct and the file exists Some URLs may not be directly accessible for download
403 Error (Forbidden)
Some servers may block download requests The program includes User-Agent headers to mimic a web browser
Unable to Determine File Size
The program attempts multiple methods to determine the file size If all methods fail, try a different URL
Connection Issues
Ensure you have a stable internet connection Some servers may limit the number of concurrent connections
Recommended Test Files For testing your downloader, you can use these reliable sources:
ThinkBroadband Test Files: http://ipv4.download.thinkbroadband.com/10MB.zip Wikimedia Commons: https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Snake_River_%285mb%29.jpg/2560px-Snake_River_%285mb%29.jpg Apache Tomcat Binaries: https://downloads.apache.org/tomcat/tomcat-10/v10.1.17/bin/apache-tomcat-10.1.17.zip
Extension Ideas
Add GUI with progress bars Implement pause/resume functionality Add support for download retries Create a download queue manager Add bandwidth throttling options