4 ms·

In Java the Option of T type blows up the same way a NullPointerException does if you try to use the Option's value when it contains none. I agree. In Java at

• steveklabnik 7y ago
  Rust refuses to compile, because an Option<T> type is a different type than T, so if you try to use it like one, you get a type error.
  • 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 ago
      I 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.