JVM shutting down

In this chapter you will learn:

1. Exit and halt Java virtual machine
2. How to add a shut down hook

Exit and halt Java virtual machine

• void exit(int status)
  Terminates the currently running Java virtual machine by initiating its shutdown sequence.
• void halt(int status)
  Terminates the currently running Java virtual machine.

public class Main {
  public static void main(String[] args) {
    Runtime runtime = Runtime.getRuntime();
/*  j a va2 s  .c o  m*/
    runtime.exit(2);
  }
}

Shut down hook

We can add to do list for JVM shutting down. For example we can close resource or write to log file when the JVM is shutting down.

• void addShutdownHook(Thread hook) Registers a new virtual-machine shutdown hook.
• boolean removeShutdownHook(Thread hook) De-registers a previously-registered virtual-machine shutdown hook.

public class Main {
  public static void main(String[] args) {
    Runtime runtime = Runtime.getRuntime();
//from j a  v a2s.c  o  m
    runtime.addShutdownHook(new Thread(){
      public void run(){
        System.out.println("Shut down");
        
      }
      
    });
  }
}

The output:

Next chapter...

What you will learn in the next chapter:

1. How to get the number of processors available to the Java virtual machine

Java standard stream

Java system property get and set

Current time in millis second and nano second

Random UUID

JVM memory

JVM garbage collector

JVM shutting down

Processor count

OS system commands

Random class

Random value

Random value range

Compile Java source code

Timer and TimerTask