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Java would also refuse to compile using an Optional<T> where T is expected. Java and Rust are practically the same regarding the differences between Optional<T
by swsieber 7y ago
Java would also refuse to compile using an Optional<T> where T is expected.
Java and Rust are practically the same regarding the differences between Optional<T> and T (java), and Option<T> and T (rust). Optional<String> in Java has the `.get()` method which corresponds to the `.unwrap()` method in Rust. And in both are different different types than String in their respective languages.
But in Java you can have an Optional<String> that's null, not just empty. So that's three states - null, wrapping null, or wrapping a value.
I'd say the big difference is that in Rust you can have places that refuse nulls (e.g. using T instead of Option<T>), so you have well defined points of control/checking. That, combined with the difficulty in recovering from a panic (the equivalent of a null pointer exception when trying to unwrap a value that's missing) and the Result type, are Rusts real strength wrt. missing values.
- steveklabnik 7y agoI think we are saying the same thing, from slightly different perspectives. That Option can be nullable means that it can be used where it is not actually that type, without a type error, is what I’m saying.