@Override
      public ScheduledFuture<?> schedule(final Runnable command, final long delay,
          final TimeUnit unit,
          final ScheduledExecutorService scheduledExecutorService,
          final ExecutionContext executionContext) {
        return scheduledExecutorService.schedule(command, delay, unit);
      }
This enum (an abstract base class or ABC) and its enum constants (subclasses of the ABC)
play the role of "ConcreteState" classes in the GoF "State" pattern.

See {@link MemoryState} for details.
geode-core/src/main/java/org/apache/geode/cache/query/internal/QueryMonitor.java