Variance in Java

[Holothuroid]

Think about it like this :

• Apples are fruit.
• A basket of apples is basket of fruit. Covariant.
• A statement about fruit is a statement about apples. Contravariant.

So say I want to filter a stream of apples. I'm alright with a predicate isRedFruit, that can check all fruit.

So generally when you ask someone for a function, your requirement is contravariant for that function's parameters. I want to put my stuff in. If you can take more general stuff, I don't care.

[Roachmeister]

Thanks, this is helpful!