Java process inputstream to file

What if we just want to list the contents of a directory? A simple way to do this is by invoking the Files. As shown in the above example, we can use the Files::IsRegularFile operation to list only the regular files.

What if we need to visit the subdirectories too? In the above example, we filter the stream returned by the Files. In the previous example, we saw how we can filter stream obtained from the Files. There is a more efficient way of doing this by using the Files. The corresponding Path object is included in the returned stream if the BiPredicate returns true. Let us look at an example to see how we can use the find method to find all PDF files anywhere within the given depth of the root folder:.

In the above example, the find method returns a stream with all the regular files having the. The depth parameter is the maximum number of levels of directories to visit. A value of 0 means that only the starting file is visited, unless denied by the security manager. The JarFile. Entries appear in the stream in the order they appear in the central directory of the ZIP file.

So how do we iterate through the entries of the JAR file? Here is an example which demonstrates this:. Once we get the stream from the JAR file, we can always perform a filtering operation to get the matching JarEntry objects:.

So the output will be as follows. In this article, we discussed how to generate Java 8 streams from files using the API from the java. Files class. When we manage data in files, processing them becomes a lot easier with streams.

A low memory footprint due to lazy loading of streams is another added advantage. We saw that using parallel streams is an efficient approach for processing files, however we need to avoid any operations that require state or order to be maintained. To prevent resource leaks, it is important to use the try-with-resources construct, thus ensuring that the streams are automatically closed.

We also explored the rich set of APIs offered by the Files class in manipulating files and directories. The example code used in this article is available on GitHub. Graphics; import java. Graphics2D; import java. File; import java. IOException; import java. InputStream; import java. List; import javax. JFrame; import javax.

JPanel; import javax. JScrollPane; import javax. JTextArea; import javax. SwingWorker; import javax. UIManager; import javax. MadProgrammer MadProgrammer k 22 22 gold badges silver badges bronze badges. There was no mention of a JTextArea?

Are you executing the process within in the EDT? Sorry, yes I realise that this was the crucial part causing the issue as I commented earlier. Code borrowed for this answer to a similar question. Many thanks! Add a comment. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back 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.