java Multithreading using Executor

Question

I have 2 classes that implement Runnable.I need to create 10 threads to execute them.I use the following code.

ExecutorService es = Executors.newFixedThreadPool(10);
  Runnable r=new TestThread1();
  Runnable r1=new TestThread2();
  es.execute(r);
  es.execute(r1);

but since only 2 runnables exist,only 2 threads are being used to execute.how shud i increase the no of threads

Do you mean that you want to run each Runnable on 5 threads? — Rich
– Rich, Commented Jan 27, 2011 at 8:26
I've a feeling that you want to make one runnable use multiple threads - that can't happen. To 'spread' a task over multiple threads, you need to re-write the code. — Highland Mark
– Highland Mark, Commented Jan 27, 2011 at 13:56

Vijay Mathew · Accepted Answer · 2011-01-27 08:30:12Z

3

Threads will be created as you submit more jobs to the executor. If the number of submitted jobs exceed 10 (in this case), the new jobs will be queued. When threads become free they will be used to run the queued jobs. If you want the executor to create 10 threads, you need to submit 10 jobs:

for (int i = 0; i < 5; ++i) {
    if (!es.isShutdown()) {
        es.submit(new TestThread1());
        es.submit(new TestThread2());
    }
}

answered Jan 27, 2011 at 8:30

Vijay Mathew

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2 Comments

ish Over a year ago

I have a few database insert statements in 2 runnable classes.As jobs are inside a loop iterated 5 times,i ve each value being inserted 5 times.i want this to be avoided

Peter Lawrey Over a year ago

You shouldn't need to check whether its shutdown as the ExecutorService has a rejection policy which you can change to handle this case.

dogbane · Accepted Answer · 2011-01-27 08:29:28Z

1

One Runnable can only run on one Thread. It doesn't get split up across multiple threads automatically.

If you want to utilise your entire thread pool, create more runnable objects.

answered Jan 27, 2011 at 8:29

dogbane

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Comments

卢声远 Shengyuan Lu · Accepted Answer · 2011-01-27 09:44:46Z

0

Executors.newFixedThreadPool(size) returns ThreadPoolExecutor instance.

JavaDoc of ThreadPoolExecutor says: ” When a new task is submitted in method ThreadPoolExecutor.execute, and fewer than corePoolSize threads are running, a new thread is created to handle the request, even if other worker threads are idle.”

That is, you have to execute 10 threads to fill the pool.

answered Jan 27, 2011 at 9:44

卢声远 Shengyuan Lu

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