code: public static List<Message> checkBackwardCompatibility(Schema oldSchema,
                                                             Schema newSchema,
                                                             String name) {
          SchemaEvolutionValidator validator = new SchemaEvolutionValidator();
          List<Message> messages = new ArrayList<Message>();
          validator.compareTypes(oldSchema, newSchema, messages, name);
          return messages;
      }
docs: Compare two schemas to see if they are backward compatible. Returns a
  list of validation messages. <li>ERROR messages indicate the schemas are
  not backward compatible and the new schema should not be allowed. If an
  ERROR schema is uploaded, clients will not be able to read existing data.
  <li>WARN messages indicate that the new schemas may cause problems for
  existing clients. However, once all clients are updated to this version
  of the schema they should be able to read new and existing data. <li>INFO
  messages note changes to the schema, basically providing a friendly list
  of what has changed from one version to the next. This includes changes
  like the addition of fields, changes to default values, etc.
  
  @param oldSchema the original schema
  @param newSchema the new schema
  @param name the schema name
  @return list of messages about the schema evolution