How to download a file java

There are multiple ways to download a file using Java code. Here are just a few ways of how you can accomplish the task:. The most easily available and a basic package available for downloading a file from internet using Java code is the Java IO package.

Here we will be using the BufferedInputStream and the URL classes to open and read a file on a given address to a file on our local system. The reason we use the BufferedInputStream class instead of the InputStream is its buffering ability that gives our code a performance boost. Before we dive deeper into the coding aspect let's take an overview of the classes and the individual functions we will be using in the process.

The java. URL class in Java is a built-in library that offers multiple methods to access and manipulate data on the internet. In this case, we will be using the openStream function of the URL class. The method signature for the openStream function is:. The openStream function works on an object of the URL class. The URL class opens up a connection to the given URL and the openStream method returns an input stream which is used to read data from the connection. These classes are used for reading from a file and writing to it, respectively.

The contents are read as bytes and copied to a file in the local directory using the FileOutputStream. To lower the number of lines of code we can use the Files class available from Java 7. The Files class contains methods that read all the bytes at once and then copies it into another file. Here is how you can use it:.

Java NIO is an alternative package to handle networking and input-output operations in Java. The main advantage that the Java NIO package offers is that it's non-blocking, and has channeling and buffering capabilities.

When we use the Java IO library we work with streams that read data byte by byte. However, the Java NIO package uses channels and buffers. The buffering and channeling capabilities allow the system to copy contents from a URL directly into the intended file without needing to save the bytes in application memory, which would be an intermediary step.

The ability to work with channels boosts performance. The downloaded contents will be transferred to a file on the local system via the corresponding file channel. After defining the file channel we will use the transferFrom method to copy the contents read from the readChannel object to the file destination using the writeChannel object.

The transferFrom and transferTo methods are much more efficient than working with streams using a buffer. The transfer methods enable us to directly copy the contents of the file system cache to the file on the system. Thus direct channeling restricts the number of context switches required and enhances the overall code performance. Now, in the following sections, we will be looking at ways to download files from a URL using third-party libraries instead of core Java functionality components.

Now you may be thinking why would we use this when Java has its own set of libraries to handle IO operations. However, Apache Commons IO overcomes the problem of code rewriting and helps avoid writing boilerplate code. In order to start using the Apache Commons IO library, you will need to download the jar files from the official website. When you are done downloading the jar files, you need to add them to use them.

If you are using an Integrated Development Environment IDE such as Eclipse , you will need to add the files to the build path of your project. There is only a single line of code required to download a file, which looks like:.

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. The next best way to download a file from an online source is to use the FileUtils. 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. Just like the first example, we use the java. 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. Download a File Using the java. FileOutputStream; import java. IOException; import java. URL; import java.

Channels; import java.