lock().Config.makeDefaults() method.Config instance.Configurable interface is meant to be used as an interface / paradigm for any class that separates
construction-time configuration methods from the rest of the instance's lifecycle.lock() only once in the lifetime of the
instance.Config.locked() that cannot be overridden, meaning that a call to this method is sure to do what the
implementation in Config specifies, so that extending classes cannot avoid the exception by overriding
Config.locked().Config abstract class.