Covariance and contravariance computer science - Eiffel. In Eiffel you can get compiler errors, because polymorphism breaks. Covariance and contravariance computer science - Java. Return type covariance is implemented in the Java programming language version 1.5. Parameter types have to be exactly the same (invariant) for method overriding, otherwise the method is overloaded with a parallel definition instead. < ...

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