static block/clause which can be used for static initializations of a class.
The code inside static block is executed only once when you load the class first time (creating object or static variable initialization).
Develop an application which runs only on Windows if user is using operating system operating system then the application will terminates.
Check what operating system is installed on user machine?
We are using getenv() method of System class which returns value of environment variable name of which is passed an as argument to it. Windows_NT is a family of operating systems which includes Windows XP, Vista, 7, 8 and others.