code: public void registerDeleteModifier(DeleteActionModifier deleteActionModifier) {
      int currentIndex = deleteActionModifiers.indexOf(deleteActionModifier);
      if(currentIndex == -1) {
        deleteActionModifiers.add(deleteActionModifier);
      } else {
        deleteActionModifiers.set(currentIndex, deleteActionModifier);
      }
    }
docs: Register a DeleteActionModifier to be called before every Delete is
  executed on HBase. This DeleteActionModifier will be replaced if already
  registered and added if its not. Equality is checked by calling the equals()
  on the deleteActionModifier passed. DeleteActionModifiers will be called
  in the order they are added, so if any modifier is destructive,
  it must be added in the right order.
  
  Not Thread Safe
  @param deleteActionModifier The DeleteActionModifier to register.