Java
Generics Variance: Covariance, Wildcards, and PECS
Wildcard generics confuse most developers on sight, but the PECS rule turns a wall of question marks into a mechanical, memorable decision.
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Wildcard generics confuse most developers on sight, but the PECS rule turns a wall of question marks into a mechanical, memorable decision.
Generics keep the type information any throws away — how to write them, constrain them with extends, and know when a plain union is the better call.