如何使用ExecutorCompletionService

Question

I would like to use the constructor on the ExecutorCompletionService which takes a pre-defined BlockingQueue .

Can anyone provide a code snippet to show how this is done. It seems only to take aa BlockingQueue with Future s. How does this match with the fact that submit must be done with Callable s.

I'm getting a little confused here - please help...

Answer 1

ExecutorCompletionService的Javadoc中包含一个大型代码示例，而记录在案的构造函数采用BlockingQueue 。

Answer 2

The Callables supplied to submit() will be wrapped up internally as FutureTask s, and it's those (or a wrapper around one) that will eventually be inserted into the provided queue. That's all an implementation detail, though. (And, note, that this use case of inserting the outcome into the queue is the main reason why there's a protected done() method in FutureTask .) The contract says that result-yielding functions go in, and eventually results come out. The Future s drawn from the queue represent the eventual outcomes of the functions you submitted earlier.