如何声明Callable执行函数在Java中返回void？

Question

Suppose I would like to run static method foo asynchronously

void foo() throws Exception {...} 

Since foo throws an exception I would prefer create a Callable and invoke ExecutorService.submit with it to get a Future .

Now I wonder how to declare those Callable and Future properly. Should I declare them

Callable<Void> and Future<Void>?

Answer 1

Should I declare them Callable<Void> and Future<Void> ?

Yes.

Void is similar to the wrapper classes Integer , Long etc. for the primitive types int , long etc. You could say it's a wrapper class for void , even though void is not really a type.

Answer 2

I think you should declare them Callable<?> and Future<?> . Then you can implement them anyway you want including Callable<Void> and Future<Void> .