Does singleton design pattern make sure one single object reference or there is any chance/possibility of more then one ref of an object while implementing singleton pattern, I think in the case of multi threading there is a some chance of more then one object even we have implemented singleton pattern.
Please help.
It is possible for threading to cause problems with a singleton. You can find a comprehensive set of solutions for making singletons thread safe here:
A singleton pattern is a design pattern that restricts the instantiation of a class to one object. If an instance already exists, it simply returns a reference to that object. However in a multithreaded environment it is possible that 2 separate threads may enter getInstance() simultaneously, check that instance is null and then create 2 instances of the class. Hence in order to prevent it you need to mark your getInstance() as synchronized as in:
public static synchronized Singletone getInstance() {
if(instance == null){
instance = new createInstance();
}
return instance;
}
Check out this post for a better understanding .
Singleton pattern ensures a single object is created in an application running on a JVM. This holds true even in Multithreaded environment. If not, that's not Singleton or at least badly programmed Singleton.
When you have singleton class, you can't create more then one object of that class. You may create many reference on that object, but object will be same.
