9. List map
scala> list.map((i: Int) => i * 2)
---
java
List<Integer> result = new ArrayList<>();
for(int i = 0; i < list.size; i++) {
result.add(list.get(i) * 2);
}
10. List map
scala> list.map((i: Int) => i * 2)
scala> list.map(_ * 2)
scala> val f = (i: Int) => i * 2
scala> list.map(f)