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javaexecutorservice
Matt Ball
Matt Ball

Reputation: 360046

Will a ScheduledExecutorService create new threads as needed?

I'm using Executors.newScheduledThreadPool() to create a ScheduledExecutorService, specifying the number of threads like so:

int corePoolSize = 42;
ScheduledExecutorService foo = Executors.newScheduledThreadPool(corePoolSize);

According to the JavaDocs, the corePoolSize argument sets

the number of threads to keep in the pool, even if they are idle.

Does this mean that this ExecutorService implementation may create more than corePoolSize threads as needed, similar to a cached thread pool?

Upvotes: 16

Views: 12452

Answers (2)

Michael
Michael

Reputation: 304

No. The correct answer is no, a ScheduledExecutorService will not spawn new threads.

See answer here

Upvotes: 14

oxbow_lakes
oxbow_lakes

Reputation: 134340

Does this mean that this ExecutorService implementation may create more than corePoolSize threads as needed?

Yes, that is exactly what it means. The reason for the existence of corePoolSize is the expense of thread-creation. If you expect to be firing large numbers of short-lived tasks at your executor service, you may expect to find, at a given point in time, large numbers of idle threads.

Rather than have these threads die, only to be replaced a very short time later by newly-created threads, corePoolSize will ensure that there will always be a number of spinning threads.

Upvotes: 6

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