CODEWITHSUNDEEP
javamultithreadingspring-bootexecutorservicethreadpoolexecutor
itro
itro

Reputation: 7228

Why thread in spring boot using ExecutorCompletionService does not start in parallel?

I use spring boot version 2.1.9.RELEASE along with Java 1.8 and have two lang running processes which I wanted to be started in parallel. Therefore I have decided to use thread. When I start the sumResult method, the second thread starts first and the first thread wait until the second one is finished.

Why these two threads does not start at the same time or at least short after each other?

private void sumResult(String year, String month, String day) throws 
    ExecutionException, InterruptedException {
         ExecutorCompletionService<Boolean> completionService = new 
         ExecutorCompletionService<>(Executors.newCachedThreadPool());

         // First thread
         mut.initialise(year, month, day);
         boolean mutCompleted = completionService.submit(
               ()-> mut.sum(),true).get();

         // Second thread
         apt.initialise(year, month, day);
         boolean aptCompleted = completionService.submit(
              ()-> apt.sum(), true).get();

         // On completion of both thread
         if(mutCompleted && aptCompleted ){
              mixAndPrint();
         }

}

Upvotes: 0

Views: 244

Answers (1)

Thilo
Thilo

Reputation: 262504

Because you are blocking on calling get() on the first job before even submitting the second one.

submit
get
submit
get

If you want them to run in parallel, you need to do

submit
submit
get
get

Upvotes: 4

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