synchonized? correct use? Thread-safe Singleton

[BLS]

Do I have a THread-safe singleton ? If not HowTo..   Sorry. Sean K 
allready explains it to me, but I 've lost the info. :(
Bjoern

class Singleton(T)
{
   public:
   static T instance()
   sychronized       // according to the language spec this should work
   {
     if(_instance is null) _instance = new T;
     return _instance;
   }

   private:
   this() {}

   static T _instance;
}

class Application : Singleton!(Application)
{
}