"Static typing" is not quite where those come from – mapTo{Int,Long,Double} exist because of Java's primitive/object dichotomy. You can just write map and do the same calculation, but then your lambda will have type ? -> Long (vs. the http://docs.oracle.com/javase/8/docs/api/java/util/function/... , which provides ? -> long).
It's mostly the same semantics, but it costs an extra object for each element in your list. If the only thing you're going to do is sum those longs or serialize them over the wire or something, the extra 6 characters have a significant impact on run-time. There's lots of solutions in this space (e.g. Rust is a static language that uses a lot of "zero-cost" abstractions like tagged pointers that it can prove are safe specifically because of the static types), but Java's "make the programmer do it explicitly" isn't so bad for 1995.
It's mostly the same semantics, but it costs an extra object for each element in your list. If the only thing you're going to do is sum those longs or serialize them over the wire or something, the extra 6 characters have a significant impact on run-time. There's lots of solutions in this space (e.g. Rust is a static language that uses a lot of "zero-cost" abstractions like tagged pointers that it can prove are safe specifically because of the static types), but Java's "make the programmer do it explicitly" isn't so bad for 1995.