executorservice - How is an executor terminated in my Java program? -


this question related previous question : why speed of java process inside multiple loops slows down goes?

in order find problem of question, looked closely @ code , found executors in app not terminated, since i'm in process of learning how use executors, copied online sample codes , used them in app, , i'm not sure if i'm using them correctly.

what's difference between following 2 approaches of using executors ?

[1]

 executor executor=executors.newfixedthreadpool(30);  countdownlatch donesignal=new countdownlatch(280);   (int n=0;n<280;n++)  {    ...    executor.execute(new samplecountrunner(donesignal,...));  }  try { donesignal.await(); }  catch (exception e) { e.printstacktrace(); }

[2]

executorservice executor=executors.newfixedthreadpool(30);  (int i=0;i<60;i++) {   ...   executor.execute(new xyzrunner(...)); } executor.shutdown();  while (!executor.isterminated()) { }

it seems me after 1st 1 done, executor still has active pool of threads running , waiting more tasks, consume cpu time , memory.

the 2nd 1 terminate active threads in pool after shutdown() method run, , active threads won't take more cpu time or memory after point.

so questions :

[1] correct ?

[2] how terminate pool of threads in 1st case ? there no "executor.shutdown()" executor

edit :

problem solved, changed executor in [1] executorservice, , added :

   executor.shutdown();    while (!executor.isterminated()) { }

now when program ends, won't have lot of threads active more.

it seems me after 1st 1 done, executor still has active pool of threads running , waiting more tasks, consume cpu time , memory.

not exactly. in first approach , after tasks done ( signalled latch ) , executor not shutdown - threads in executor not consume cpu ( consume minimum memory needed thier structures yes ).

in approach - explicitly in control of knowing when , how tasks completed. can know if tasks have succeeded or failed , , can decide resubmit tasks if needed.

the 2nd 1 terminate active threads in pool after shutdown() method run, , active threads won't take more cpu time or memory after point.

again ,not .in approach , executorservice not shutdown after call shutdown(). waits submitted tasks complete , here not directly know if these tasks completed or failed ( throwing exception ).

and until submitted tasks completed - isshutdown() tight loop ( spike cpu near 100% ) .


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