In FP, we only use val. In OOP, always use val unless there's a good reason not to.
Scala uses the CamelCase naming style: val firstName = "Alvin".
Explicitly declaring data types: val x = 1 // implicit, val x: Int = 1 // explicit, val x: Long = 1 // explicit.
Especially in an IDE, you generally don't need to show the type explicitly, thanks to syntax highlighting.
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