code: public static <T> T checkNotNull(T reference) {
      return com.google.common.base.Preconditions.checkNotNull(reference);
    }
docs: Ensures that an object reference passed as a parameter to the calling method is not null.
  
  @param reference an object reference
  @return the non-null reference that was validated
  @throws NullPointerException if {@code reference} is null