code: public static void checkNotNull(String parameterName, Object object) {
          if (object == null) {
              throw Exceptions.IllegalArgument("Input %s can't be null.",
                      parameterName);
          }
      }
docs: Check that the parameter is not {@code null}.
  
  @param parameterName
  The name of the user-supplied parameter that we are validating
  so that the user can easily find the error in their code.
  @param object
  The parameter object can be any Java reference type, including
  arrays.
  @throws IllegalArgumentException
  If the object is null pointer.