code: public static void checkNotNull(Object param, String errorMessagePrefix) throws
              IllegalArgumentException {
          checkArgument(param != null, (errorMessagePrefix != null ? errorMessagePrefix :
                  "Parameter") + " must not be null.");
      }
docs: Check that a parameter is not null and throw IllegalArgumentException with a message of
  errorMessagePrefix + " must not be null." if it is null, defaulting to "Parameter must not be
  null.".
  
  @param param              the parameter to check
  @param errorMessagePrefix the prefix of the error message to use for the
  IllegalArgumentException if the parameter was null
  @throws IllegalArgumentException if the parameter was {@code null}