How ExecutorCompletionService 's submit (Callable) method works ..

Question

How the submit() works?
My doubt is ..if i submit 5 tasks by calling 5 times the submit method one by one,
Will the executor call them at a time( i.e. in multiple threads) or done one by one.
If one by one fashion what one will be order of execution.
My Code is
ExecutorService executorService = Executors.newCachedThreadPool();
CompletionService< Object > completionService = new ExecutorCompletionService< Object >( executorService );
// submit all the callables
for ( Callable< Object > callable : callables )
completionService.submit( callable );
for ( int i = 0; i < callables.size(); i++ )
try
// execute the delete for this control point table
completionService.take().get();
catch ( InterruptedException e )
// ignore interruptions
catch ( ExecutionException e )
// log each error but continue processing
log.error( "Error deleting file data", e );
exceptions = true;
My doubt is when it starts execution after submit().. or when calling take().get()...?
Please help me ..
thanks,
Venkat

Answer 1

How the submit() works?
My doubt is ..if i submit 5 tasks by calling 5 times
the submit method one by one,
Will the executor call them at a time( i.e. in
multiple threads) or done one by one.Depends on the ExecutorService that the ExecutorCompletionService is using. You are using a thread pool that has multiple threads so your tasks will be executed simultaneously.
If one by one fashion what one will be order of
execution.See above.
>
My Code is
ExecutorService executorService =
Executors.newCachedThreadPool();
CompletionService< Object > completionService
= new ExecutorCompletionService< Object >(
executorService );
// submit all the callables
for ( Callable< Object > callable : callables )
completionService.submit( callable );
int i = 0; i < callables.size(); i++ )
try
// execute the delete for this control point
table
completionService.take().get();
catch ( InterruptedException e )
// ignore interruptions
catch ( ExecutionException e )
// log each error but continue
processing
log.error( "Error deleting file data",
e );
exceptions = true;
y doubt is when it starts execution after submit()..Correct
or when calling take().get()...?No