import org.apache.log4j.Category;
import org.apache.log4j.Priority;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.ConsoleAppender;
import org.apache.log4j.spi.LoggingEvent;
 
/**
  * This class tends to show that the <code>finalize</code>r are effectively 
  * run, but no <code>finalize</code>r of the unreachable chains of 
  * <code>Object</code>s are GCed.
  * 
  * In its current state the program should not show anything in the console
  * 
  * <pre>    
  *       public class FinalizedClass
  *       {
  *         public Category log;
  *         
  *         public FinalizedClass ()
  *         {
  *           log = Category.getInstance(FinalizedClass.class);      
  *         }
  *         
  *         public void finalize()
  *         {
  *           log.warn("finalize() run");
  *         }
  *       }
  * </pre>      
  * 
  * The code has been successfully tested on the JDK's 1.2.2, 1.3, 1.4  
  * 
  * @author <a href="mailto:tsmets@lautre.net">Thomas SMETS</a>
  * @version 0.3 - final
  * 
  */
public class ThreadedExampleWithoutGC
  implements Runnable
{
  public Category log;
  public int i;
  
  public static final int SLEEP_TIME = 1000;
  public static final int SPAWN_EVERY = 100;
  public static final int ARRAY_SIZE = 100000;
  
  ThreadedExampleWithoutGC (int i)
  {
    log = Category.getInstance(ThreadedExampleWithoutGC.class);
    this.i = i;
    log.info ("ThreadedExampleWithoutGC " + i + " created");
  }
    
  public void run()
  {    
    int j = 0;
    int k;
    FinalizedClass o[];
    while (true)
    {
      o = new FinalizedClass[ARRAY_SIZE];  // Allocate the space for the Object
      try 
      {
        log.info("Hi, I am " + i + " this is my " + j++ + "th loop");
        for (k = 0; k < ARRAY_SIZE; k++)         
          o[k] = new FinalizedClass();    // 
        
        Thread.sleep(SLEEP_TIME);
      }
      catch (Exception ex) 
      {
        log.warn("Ooops I got an exception", ex);
      }
      
      for (k = 0; k < ARRAY_SIZE; k++)       // Simply dereferences the Custom Object
        o[k] = null;      
    }
  }
  
/**
  * The provided implementation of the finalize method simply allow 
  * to put Logging statement in it !   
  */    
  public void finalize ()
  {
    log.warn ("Running the finalizer for ThreadedExampleWithoutGC number " + this.i);
  }  
  
  public static void main (String[] args)
    throws Exception
  {
     int i = 0;
     BasicConfigurator.resetConfiguration();
     //BasicConfigurator.configure(new CustomConsoleAppender(Priority.INFO));
     BasicConfigurator.configure ();
     System.runFinalization();
     Thread t =null;
     do             // This "infinite" do-loop will generate java.lang.OutOfMemoryError
     {              // The program is therefore bound to crash before some of 
        try         // the finalizer are run
        {
          t = new Thread(new ThreadedExampleWithoutGC(i++));
          t.start();
          Thread.sleep(SPAWN_EVERY);
          t = null; // To make sure that no reference to the active Thread still exist.
        } catch (Exception ex) 
        { // Just in case the System runs out of Memory
          System.out.print("Exception " + ex.getClass());
        }        
     } while (true);       
  } // End of main
  
  /**
    * This class is there simply to allow an <code>Object</code> finalization 
    * to be logged with its own <code>Level</code> and space of logging.
    */
  public class FinalizedClass
  {
    public Category log;
    
    public FinalizedClass ()
    {
      log = Category.getInstance(FinalizedClass.class);      
    }
    
    public void finalize()
    {
      log.info("finalize() run");
    }
  } // End of inner class FinalizedClass
  
  /**
    *
    * This class allows for a quickly <i>custom logging</i> to the Console.
    * Any statement above the <code>Priority</code> level passed as
    * argument ot the constructor will be given to the parent 
    * <code>ConsoleAppender</code> for Logging.
    * 
    * I took this approache as I am not used to <code>PropertyConfigurator</code>, 
    * yet.
    * 
    * (Inner) Class is <code>static</code> for simplicity's sake. 
    * 
    */
  static class CustomConsoleAppender 
    extends ConsoleAppender
  {     
    Priority LoggingPriority = null;
    
    CustomConsoleAppender(Priority aLoggingLevel)
    {
      LoggingPriority = aLoggingLevel;
    }
    
    public void doAppend(LoggingEvent aLoggingEvent) 
    {
      if (aLoggingEvent.level.isGreaterOrEqual(LoggingPriority))
        super.doAppend(aLoggingEvent);
      return;    
    }
  } // End of Inner class CustomConsoleAppender 
}   // End of Class