code: public static void checkNullArgument(Object obj, String variableName) {
      if (null == obj) {
        throw new NullPointerException(ExceptionMessageMap.getMessage("000003")
            + "  { variableName=[" + variableName + "] }");
      }
    }
docs: Performs a null check on the specified object. If the object is null, a
  <code>NullPointerException</code> is thrown.
  
  @param obj
  The object to check.
  @param variableName
  The name of the variable being checked; for use in exception messages.