@Override
  public Result postAppend(ObserverContext<? extends RegionCoprocessorEnvironment> e, Append append,
    Result result) throws IOException {
    ctPostAppend.incrementAndGet();
    return null;
  }
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