code: public void registerPutActionModifier(PutActionModifier putActionModifier) {
      int currentIndex = putActionModifiers.indexOf(putActionModifier);
      if(currentIndex == -1) {
        putActionModifiers.add(putActionModifier);
      } else {
        putActionModifiers.set(currentIndex, putActionModifier);
      }
    }
docs: Register a PutActionModifier to be called before every Put is executed on
  HBase. This PutActionModifier will be replaced if already registered and
  added if not. Equality is checked by calling the equals() on the
  putActionModifier passed. PutActionModifiers 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 putActionModifier The PutActionModifier to register.