java 8 lambda ambiguous runnable and callback

Question

Executors.newFixedThreadPool(3).submit(() -> {doSmth();});

"Ambiguous method call. Both submit (Callable) in ExecutorService and submit (Runnable) in ExecutorService match."

How to fix it? I know that I can use anonymous class but I'd like to use Function.

Works at my IDE (IntelliJ) w/o a problem. Furthermore, if `doSmth` is an instance method, you can rewrite this as `Executors.newFixedThreadPool(3).submit(this::doSmth);` — Smutje, Nov 20 '14 at 07:27
What IDE/compiler? Are you sure your lambda has a block body? (`{doSmth();}` and not `doSmth()`.) Could be a bug. — Radiodef, Nov 20 '14 at 07:56
Check whether this is your issue: http://stackoverflow.com/q/23430854/2711488 — Holger, Nov 20 '14 at 09:29
I don't think this is the same as the linked duplicate, since that was a JDK bug, and this is a "resolve ambiguity" issue... — rogerdpack, Nov 23 '16 at 18:26

Sergey Morozov · Accepted Answer · 2019-01-14T07:41:11.470

13

Executors.newFixedThreadPool(3).submit(() -> 1); //Callable
Executors.newFixedThreadPool(3).submit(() -> {doSmth();}); //Runnable

edited Jan 14 '19 at 07:41

answered Nov 20 '14 at 07:27

Sergey Morozov

1

`Executors.newFixedThreadPool(3).submit(()-> 1);` is sufficient for the Callable. – Robert Jan 11 '19 at 15:01

score 3 · Answer 2 · answered Nov 20 '14 at 07:58

3

In ambiguous cases explicitly provide the type:

Runnable runnable = () -> {doSmth();}
submit(runnable);
//or:
submit((Runnable) () -> {doSmth();});

answered Nov 20 '14 at 07:58

McDowell

4

It shouldn't be necessary, though. The OP has a block body so for it to be a `Callable` it needs to explicitly return a value. – Radiodef Nov 20 '14 at 08:12

2 Answers2