Fork Join Framework

Fork Join technology was introduced with Java version 7, to be able to deal with parallel concurrency.

This technology is based in splitting a task recursively until it is small enough to be performed. The sub-tasks will be executed in parallel in different threads. When the sub-tasks have finished, then a join is invoked to merge the results into one.

Example. The following example is very simple. It consists on a function that calculates consecutive natural numbers in an interval. The class will receive two parameters (number min. and max.). If this interval is greater than 6 (in the example) the task will be split into two sub-tasks.

The class extends RecursiveTask<Long> and implements method compute(). As our class is a task it will be invoked by ForkJoinPool



Output console:
Splitting task
Computing
Result1: 21
Computing
Result1: 57
Result2: 78

Java 7 - NIO - Watcher implementation

One of the new features of Java7 was NIO package. 
Java NIO also known as new input output library as is a set of classes defined under package java.nio.* to access files, file attributes and file systems.

The main classes from this package are:

• Path - to manage file location and directory hierarchy
• Files - to manage file operations

Some functionalities that can be implemented are:

• Walking the file tree
• Watchers - monitoring the creation/modification/deletion of files
• Copy/Create/Delete files from a directory(atomic operations with synchronization)
• Find files using matcher expressions

In the following example we are going to see how to implement a watcher. This is useful when we need a process to monitor when a file is created/modified or deleted in a directory.

Steps in this example:

1- watch for new files in a directory

2- evaluate the mime type of the file

3- if it is a text file it will be copied to other directory.