java - How to calculate run-time for a multi-threaded program? -

i trying test performance (in terms of execution time) webcrawler having trouble timing due multi-threading taking place.

my main class:

class webcrawlertest {     //methods , variables etc     webcrawlertest(list<string> websites){     //     }      if(!started){         starttime = system.currenttimemillis();         executor = executors.newfixedthreadpool(32); //this value i'm tweaking         started=true;     }            for(string site : websites){         executor.submit(webprocessor = new allwebsiteprocessortest(site, deepsearch));     }                                    executor.shutdown();     //tried grabbing end time here no luck 

allwebsiteprocessortest class:

class allwebsiteprocessortest implements runnable{     //methods , var etc      allwebsiteprocessortest(string site, boolean deepsearch) {     }     public void run() {                  scansinglewebsite(websites);         for(string email:emails){             system.out.print(email + ", ");         }  private void scansinglewebsite(string website){     try {         string url = website;         document document = jsoup.connect(url).get();         grabemails(document.tostring());     }catch (exception e) {} 

with class (with main method), create instance of webcrawlertest , pass in array of websites. crawler works fine can't seem figure out how time it.

i can start time (system.getcurrenttime...();), problem end time. i've tried adding end time this:

//another class  public static void main(.....){     long start = getcurrent....();     webcrawlertest w = new webcrawlertest(listofsites, true);     long end = getcurrent....(); } 

which doesn't work. tried adding end after executor.shutdown(), again doesn't work (instantly triggered). how grab time final completed thread?

after shutting down executors pool

executor.shutdown(); //tried grabbing end time here no luck 

you can

executor.awaittermination(timeunit, value) 

this call block untill tasks completed. take time, subtract t0 , voila, have execution time.

shutdown() method assures no new tasks accepted excution queue. tasks in queue performed (shutdownnow() drops pending tasks). wait running tasks complete, have awaittermination().