package app.utils 
{	
	public class Singelton
	{
		
	private static const m_instance:Singelton = new Singelton(SingeltonLock);
		
		public function Singelton(lock:Class)
		{
			if (lock != SingeltonLock)
			{
				throw new Error("Singelton can only be accessed through Singelton.getInstance().");
			}
			
		}

		private static function get instance():Singelton
		{
			return m_instance;
		}	
	}
}

internal class SingeltonLock 
{
}

Singelton template

ActionScript 3