Java Runtime Class

Introduction

The Java Runtime class allows the application to interface with the environment in which the application is running.

Class Declaration

Following is the declaration for java.lang.Runtime class −

public class Runtime
   extends Object

Class methods

Methods inherited

This class inherits methods from the following classes −

• java.lang.Object

Example: Adding Shutdown Hook to a Thread Object

The following example shows the usage of Java Runtime addShutdownHook() method. In this program, we've created one static inner class Message which is extending Thread. In main method, we've registered a shutdown hook with a new Message object using addShutdownHook() method. Then we kept system to sleep for 2 seconds and then printed a closing message. As shutdown hook is registered with Message object, its run method is called when program exits.

package com.tutorialspoint;

public class RuntimeDemo {

   // a class that extends thread that is to be called when program is exiting
   static class Message extends Thread {

      public void run() {
         System.out.println("Bye.");
      }
   }

   public static void main(String[] args) {
      try {

         // register Message as shutdown hook
         Runtime.getRuntime().addShutdownHook(new Message());

         // print the state of the program
         System.out.println("Program is starting...");

         // cause thread to sleep for 3 seconds
         System.out.println("Waiting for 3 seconds...");
         Thread.sleep(3000);

         // print that the program is closing 
         System.out.println("Program is closing...");
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

Let us compile and run the above program, this will produce the following result −

Program is starting...
Waiting for 3 seconds...
Program is closing...
Bye.