Introduction ObjectInputStream can be used to de-serialize and read java objects that have been serialized and written using ObjectOutputStream. In the example below the ‘Course’ object is written to a persistent storage. The Course object contains a list of Student objects. The object writing preserves object references. We first create an object output stream that … Read more

Reading Character Streams – Classes All classes that read character stream extend java.io.Reader. The important classes are: InputStreamReader-This class reads bytes from an underlying stream and converts it to characters using a Charset. It acts as a bridge between a byte stream and character stream PipedReader- This class connects to a PipedWriter and reads characters … Read more

Reading Bytes – classes The basic class in java.io to read data is java.io.InputStream. All classes that read bytes are derived from this class. This class is extended by the following classes. Detailed examples follow later, but lets take a 10000 feet view of the classes. We will look only at the most important classes. … Read more

In this section we look at reading data from a URL, implementing a unix like ‘tail’ in java, reading a file in reverse and some other stuff. Reading from a URL Get the contents of a URL as byte array Read data from a URL and copy to a file Read data from a url … Read more

Java 7 implemented the watch service which can be used to watch changes in a directory. The watch service is thread safe and hence multiple threads can use it. Here’s a complete example of the watch service. All steps are explained in the example

Buffers are containers of data. They store bytes and other primitive java types in arrays and allow processes to read and write bytes onto them. Buffers have three important properties. 1. Position – identifies the index where the next byte will be written or read. 2. Limit – identifies the index where there is no … Read more

Introduction Traditional IO is blocking in nature. For example traditional socket connection is blocking, wherein the server waits for a client connection and once the client connection is obtained an independent thread handles the operation of the client. Java NIO introduces non blocking IO wherein a thread does not have to wait for read or … Read more

Introduction to File Locking File Locking is a mechanism by which access to a file by multiple processes can be controlled. File Locks may be mandatory or advisory. When an operating system implements advisory locking, if provides information about locks on a particular file to any process that asks for it, however it does not … Read more

The following use cases are covered in this tutorial. Listing all files in a directory Listing files of a specific type in a directory Listing files with name matching a string Walking a directory tree with handlers for each file or directory walked Introduction Java NIO introduced the walk file tree method that is extremely … Read more

File and directory Copying Copying using java.io.File To copy a file, read the data from the file using an inputstream and write to another file using an outputstream. But there are better methods for copying, so we will not spend any time on this. However, if you are interested in using this method then read … Read more