Variance concepts in the context of parametric programming with Java By Obed Rios (5/7/2023 ) Revision 1.0 Abstract In Java, the concepts of variance are related to how the type parameters of a class or interface are related to each other when the class or interface is sub-typed or implemented. The key difference between invariant and covariant in the context of Java generics is how they handle sub-typing relationships. Invariant types do not allow assignments between different type parameters, while covariant types can accept a specified type or any of its sub-types. In addition contravariance enables you to use a more general type (super type) in a generic type or method that would normally require a more specific type (sub-type). In this work, we show explicitly the concepts of variance in the context of Java Generics. Introduction Parametric variance refers to the relationship between the type parameters of a class or interface and their subtypes. It defines how subtyping is i...
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