@Override
  public boolean preCheckAndPut(ObserverContext<? extends RegionCoprocessorEnvironment> e,
    byte[] row, byte[] family, byte[] qualifier, CompareOperator compareOp,
    ByteArrayComparable comparator, Put put, boolean result) throws IOException {
    ctPreCheckAndPut.incrementAndGet();
    return true;
  }
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