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javamultithreadingexecutorserviceexecutor
Nareshreddy Barrolla
Nareshreddy Barrolla

Reputation: 67

ExecutorService behaviour when total number of task are less then number of threads allocated

If I create ExecutorService with thread pool size 10(using newFixedThreadPool) and initially only 5 tasks are running, in this case ExecutorService create 10 threads and 5 will be ideal or only 5 thread will be created.

Upvotes: 3

Views: 176

Answers (2)

second
second

Reputation: 4259

If you use ExecutorService.newFixedThreadPool(nThreads) then you will create a thread pool of size nThreads. All threads will be created and will be idle if they have nothing to do.

ExecutorSerivce creates the constructor of ThreadPoolExecutor with the parameters:

  • corePoolSize is nThreads
  • maximumPoolSize is nThreads
  • keepAliveTime is 0
  • unit is TimeUnit.MILLISECONDS
  • workQueue is a "unbound" queue LinkedBlockingQueue
    (The actual bound is: Integer.MAX_VALUE, which normal programs should never reach)

If you don't want that, you will have to create a ThreadPoolExecutor yourself.

Note that you have to use a queue with an upper-bound (that is actually reached when you run your software normally), else no new Threads will be created - because that only happens if the queue is full.

Upvotes: 1

SSP
SSP

Reputation: 2670

In this case 10 thread will be created in thread pool. Then 5 thread will be assigned to task. and other 5 will be waiting for new task to come up.

Apart from this if any of 5 running thread is completed, it will be return to pool.

Upvotes: 0

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