Why java allows not save assignment with generic types

Asked Oct 01 '19 at 16:38

Active Oct 01 '19 at 17:13

Viewed 21 times

Hello I am prepаring for ocp and can not understand why java compiler allows not save assignment? For example:

ExecutorService executorService = Executors.newSingleThreadExecutor();
Callable c = () -> 2;
Future<String> submit = executorService.submit(c);
System.out.println(submit.get().length());

Why compiler not enforce me add explicit cast:

 Future<String> submit = (Future<String>) executorService.submit(c);

Can someone explain why cast is not required?

edited Oct 01 '19 at 17:13

asked Oct 01 '19 at 16:38

Alexander Smirnov

1

`Callable c` has a raw type. Don't you think it looks odd to say that it's a `Future` when the callable returns an `int`? – Andy Turner Oct 01 '19 at 16:40
This is just example to demonstrate concept. – Alexander Smirnov Oct 01 '19 at 16:43
1

make it a non-raw type, and you'll see that it no longer compiles. – Andy Turner Oct 01 '19 at 16:43

Why java allows not save assignment with generic types

0 Answers0