Try this:-I think mapToInt() is more appropriate than straight .map() because the getAge() method will return an int. The .map() call would probably return a Stream<Integer>. Hint: use an IDE for your Streams code; hover your mouse over the method calls and it will tell you the type of Stream being returned.
As far as possible, don't create Stream<T> variables. You will occasionally have to in this sort of situation, but this is an exception:-Of course that might not compile because the something variable goes out of scope without ever being used