Singleton class for an object with parameters

Question

I realized that I should have only one instance of an object called StdSchedulerFactory running at a time. So far I instantiated the object like this

StdSchedulerFactory sf = new StdSchedulerFactory(properties);

And properties is a NameValueCollection. How can I write a Singleton class for this object so that the variable sf will always have one instance throughout the program?

Answer 1

Part of the Singleton pattern is typically a private constructor, so that other classes can not make new instances.

The workaround for parameters coming from outside the class is to add a "Init" or "Configure" function:

public static void Configure(NameValueCollection properties)
{
}

Of course, if you forget to call this function, you may get behavior you don't want; so you may want to set a "Configured" flag or something like that so your other functions can react appropriately if this function has not yet been called.