src/java.base/windows/classes/sun/nio/ch/DefaultPollerProvider.java

*** 32,11 ***
  class DefaultPollerProvider extends PollerProvider {
      DefaultPollerProvider() { }
  
      @Override
      int defaultReadPollers(Poller.Mode mode) {
!         assert mode == Poller.Mode.SYSTEM_THREADS;
          int ncpus = Runtime.getRuntime().availableProcessors();
          return Math.max(Integer.highestOneBit(ncpus / 8), 1);
      }
  
      @Override
--- 32,13 ---
  class DefaultPollerProvider extends PollerProvider {
      DefaultPollerProvider() { }
  
      @Override
      int defaultReadPollers(Poller.Mode mode) {
!         if (mode != Poller.Mode.SYSTEM_THREADS) {
+             throw new UnsupportedOperationException();
+         }
          int ncpus = Runtime.getRuntime().availableProcessors();
          return Math.max(Integer.highestOneBit(ncpus / 8), 1);
      }
  
      @Override

*** 44,15 ***
          return (fdVal >> 2) & (toIndex - 1);
      }
  
      @Override
      Poller readPoller(boolean subPoller) throws IOException {
!         assert !subPoller;
          return new WEPollPoller(true);
      }
  
      @Override
      Poller writePoller(boolean subPoller) throws IOException {
!         assert !subPoller;
          return new WEPollPoller(false);
      }
  }
--- 46,17 ---
          return (fdVal >> 2) & (toIndex - 1);
      }
  
      @Override
      Poller readPoller(boolean subPoller) throws IOException {
!         if (subPoller)
+             throw new UnsupportedOperationException();
          return new WEPollPoller(true);
      }
  
      @Override
      Poller writePoller(boolean subPoller) throws IOException {
!         if (subPoller)
+             throw new UnsupportedOperationException();
          return new WEPollPoller(false);
      }
  }