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I am not sure whether this is the right forum to ask this question, but it refers to code, so I am asking here.
In the book “Groovy in action”, section 7.1.4 (named parameters), the author says that usage of named params “crops up frequently in creating immutable classes that have some parameters that are optional”.
What has immutability of the class got to do with optional parameters? I thought these 2 topics were completely orthogonal.
The key to that statement is that if you’re dealing with an immutable class, the implication is that you have only one chance to set state – in a constructor. Normally you’d be able to manipulate an (mutable) object via setters, one-at-a-time, to build up the desired state. For an immutable, you’d have to create a ctor for every possible set of instantiation states instead, if a facility like optional params were not available. For a class with many fields, this could get messy.