ShutdownHookDemo.java

Download ShutdownHookDemo.java source file

// Demo showing a sample use of a shutdown hook.  Shutdown
// hooks replace using finializers in Java.
//
// Written 9/2006 by Wayne Pollock, Tampa Florida USA.

import java.util.*;

public class ShutdownHookDemo
{

   static List<String> resourceList = new ArrayList<String>();

   public static void main( String [] args ) throws Exception
   {
      Thread shutdownHook = new Thread() {
         public void run ()
         {
            System.out.println( "Running shutdown hook:" );
            // for each item that needs cleanup steps, do them now.
            // Note in real life you probably have a list of objects,
            // each with some "cleanup" code to run.  Each object, in
            // its constructor can register a shutdown hook.  Then you
            // don't need a list as used here.

            for ( String name : resourceList )
               System.out.println( "\tCleaning up resource " + name );
         }
      };

      Runtime currentJRE = Runtime.getRuntime();
      currentJRE.addShutdownHook( shutdownHook );

      // Now do stuff, knowing any resources will be cleaned up at exit:
      resourceList.add("Blossom" );
      resourceList.add("Buttercup" );
      resourceList.add("Bubbles" );

      System.out.print( " Type 'x' to exit, 'e' to cause exception, "
            + "or 'p' to pause: " );
      Scanner in = new Scanner( System.in );
      String choice = in.next();
      switch ( choice.charAt(0) )
      {
      case 'x':
      case 'X':   System.exit( 0 );

      case 'e':
      case 'E':   throw new Exception( "abort" );
      }

      // Sleep for a few seconds to allow user to hit ctl+c:
      try { Thread.sleep( 8*1000 ); } catch (InterruptedException e) {}
   }
}