java - How is it possible that an interface is being instantiated in this sample code? -

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• can instantiate interface in java [duplicate] 5 answers

a manual i'm reading includes example, scheduledexecutorservice being created. however, api shows scheduledexecutorservice interface, not class. how possible being instantiated?

here's sample code shown:

import java.util.concurrent.scheduledexecutorservice; import java.util.concurrent.executors; import java.util.concurrent.scheduledfuture; import static java.util.concurrent.timeunit.*;  class beepercontrol {     private final scheduledexecutorservice scheduler =     executors.newscheduledthreadpool(1);      public void beepforaminute() {         final runnable beeper = new runnable() {             public void run() {                 system.out.println("beep");             }         };          final scheduledfuture<?> future =             scheduler.scheduleatfixedrate(beeper, 250, 250, milliseconds);             scheduler.schedule(             new runnable() {                 public void run(){                 future.cancel(true);                 }             }, 3, seconds );         while (!future.isdone()) {             try {                 thread.sleep(10);             } catch(interruptedexception e) {}         }         scheduler.shutdown();     }      public static void main(string[] args)     {         beepercontrol bc = new         beepercontrol();         bc.beepforaminute();     } } 

executors.newsceduledthreadpool(int) factory method returns class implements scheduledexecutorservice interface.

edit:

as per grepcode:

        public static scheduledexecutorservice newscheduledthreadpool(                 int corepoolsize, threadfactory threadfactory) {             return new scheduledthreadpoolexecutor(corepoolsize, threadfactory);         } 

so here returning new instance of scheduledthreadpoolexecutor implements scheduledexecutorservice interface.