Rarely have I seen a class that truly needs 20 parameters, that's most often a design flaw. There might be cases where this isn't true, but those are edge cases, so it's probably also fine to apply a special patterns, such as the builder pattern.
> Rarely have I seen a class that truly needs 20 parameters
If a class seems like it needs that many parameters, it is very common that one or both of these is true:
1. It is doing too much, or
2. There are things-that-should-be-their-own-classes hiding in groups of the parameters.
#2 is kind of a subset of #1, but the "doing too much" tends to be concentrated in validating relations between parameters rather than what happens after the object is constructed.
