@Override
  public void postCloseRegionOperation(
    final ObserverContext<? extends RegionCoprocessorEnvironment> ctx, Operation op)
    throws IOException {
    if (ctPostStartRegionOperation.get() > 0) {
      ctPostCloseRegionOperation.incrementAndGet();
    }
  }
A sample region observer that tests the RegionObserver interface. It works with
TestRegionObserverInterface to provide the test case.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SimpleRegionObserver.java