docs: public static void main(String[] args) {
          if(args.length != 2) {
              System.out.println("Usage: SchemaEvolutionValidator pathToOldSchema pathToNewSchema");
              return;
          }
  
          Schema oldSchema;
          Schema newSchema;
  
          try {
              oldSchema = Schema.parse(new File(args[0]));
          } catch(Exception ex) {
              oldSchema = null;
              System.out.println("Could not open or parse the old schema (" + args[0] + ") due to "
                                 + ex);
          }
  
          try {
              newSchema = Schema.parse(new File(args[1]));
          } catch(Exception ex) {
              newSchema = null;
              System.out.println("Could not open or parse the new schema (" + args[1] + ") due to "
                                 + ex);
          }
  
          if(oldSchema == null || newSchema == null) {
              return;
          }
  
          System.out.println("Comparing: ");
          System.out.println("\t" + args[0]);
          System.out.println("\t" + args[1]);
  
          List<Message> messages = SchemaEvolutionValidator.checkBackwardCompatibility(oldSchema,
                                                                                       newSchema,
                                                                                       oldSchema.getName());
          Level maxLevel = Level.ALL;
          for(Message message: messages) {
              System.out.println(message.getLevel() + ": " + message.getMessage());
              if(message.getLevel().isGreaterOrEqual(maxLevel)) {
                  maxLevel = message.getLevel();
              }
          }
  
          if(maxLevel.isGreaterOrEqual(Level.ERROR)) {
              System.out.println(Level.ERROR
                                 + ": The schema is not backward compatible. New clients will not be able to read existing data.");
          } else if(maxLevel.isGreaterOrEqual(Level.WARN)) {
              System.out.println(Level.WARN
                                 + ": The schema is partially backward compatible, but old clients will not be able to read data serialized in the new format.");
          } else {
              System.out.println(Level.INFO
                                 + ": The schema is backward compatible. Old and new clients will be able to read records serialized by one another.");
          }
      }