The code below prints Hello World! Hello.scala file (a name of file doesn't matter) object HelloWorld { def main(args: Array[String]) { println("Hello World!") } } Key word object is used to create a singleton object. To run this script use scala interpretor (check scala command line tools ).
ShutDownHook allows you to perform operations (e.g. close opened resources, remove temporary files and so on) just before virtual machine shuts down. A documentation says that JVM may shut down in two cases: program finishes execution normally when all threads finishes their work (except deamon-threads like garbage collector) virtual machine receives a termination signal (for example after sending kill signal under unix or ctrl + C key combination under windows) Below is an example which will start endless loop which do nothing. But an important thing in this code is a part where shutDownHook is added. When an termination signal will be send to JVM a code from a run() method will be executed just before JVM shuts down. public class ShutDownHook { public static void main(String[] args) { Runtime.getRuntime().addShutdownHook(new Thread() { public void run() { System.out.println("Close opened resources"); } }); while (true) { // do nothing } } }
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