factory-method

Both Abstract Factory and Factory method patterns are creational design patterns which solves the object creation issues in different scenarios. As per GOF Factory Method pattern Define an interface for creating an object, but let the subclasses decide which class to instantiate. Factory method lets a class defer instantiation to subclass. My Understanding : Motive of the Client is to get a method present in the base Factory class get executed which is dependent upon an object whose concrete class is not known now (In such a case, either during providing the software to client, it will be

Suppose we have a generic method with such signature: T Obfuscate<T>(T value) where T : IConvertible I'm setting type constraint to IConvertible so this method can digest simple value types as well as strings. Let's forget for a moment that enums can also be supplied... I would like to avoid such implementation that would check actual parameter type to execute correct processing. // Please no GOD METHODS public T Obfuscate<T>(T value) where T : IConvertible { if (value is int) { ... } if (value is string) { ... } } This surely smells of a factory method, that would have to call particular

Why LocalDate , LocalTime , Stream , etc. objects use a factory method of() instead of a constructor? I found an explanation of why a factory methods should be used instead of new here . This answer gives a number of reasons, but the only thing that is relevant to Java Date/Time API is the following: unlike constructors, they are not required to create a new object each time they’re invoked As LocalDate and LocalTime are immutable, it probably makes sense to use a factory and reuse existing objects instead of creating a new object every time. Is it the reason why objects like LocalDate and

I'm wondering about best practice here. Is it good practice for a factory method to return null if it can't create anything? Here's an example: ICommand command = CommandFactory.CreateCommand(args); if (command != null) command.Execute(); else // do something else if there is no command An alternative would be to return a NullCommand or something, I guess, but what is best practice? I think it's potentially reasonable for a factory method to return null in some situations, but not if it's a method called CreateCommand . If it were GetCommand or FetchCommand , that might be okay... but a Create