//  SingletonClassDemo.java  (c) Kari Laitinen

//  http://www.naturalprogramming.com

//  2013-04-02  File created.
//  2013-04-02  Latest modification.

//  The following class represents a counter that
//  could be used to count collisions in a game.
//  It is also an example of a so-called singleton class
//  of which only a single object will be created with
//  the get_instance() method.

//  By using the get_instance() method different objects
//  can use the same CollisionCounter object.

class CollisionCounter
{
   private int count = 0 ;

   private static CollisionCounter instance_of_this_class = null ;

   private CollisionCounter()
   {
   }

   public static CollisionCounter get_instance()
   {
      if ( instance_of_this_class == null )
      {
         instance_of_this_class = new CollisionCounter() ;
      }

      return instance_of_this_class ;
   }

   public void increment()
   {
      count ++ ;
   }

   public int get_count()
   {
      return count ;
   }

   public void reset()
   {
      count = 0 ;
   }
}

class SingletonClassDemo
{
   public static void main( String[] not_in_use )
   {
      CollisionCounter test_counter = CollisionCounter.get_instance() ;

      test_counter.increment() ;

      CollisionCounter another_counter = CollisionCounter.get_instance() ;

      another_counter.increment() ;

      System.out.print( "\n  The count is: "
                     +  test_counter.get_count() +  "\n\n" ) ;

   }
}