Output.java

class MtgOutput{
  
  private Map<String, Object> map;
  public Output(Map<String, Object> map){
    this.map = map;
  }
  
  protected abstract String processJSONObject(JSONObject obj);
  protected abstract String processJSONArray(JSONArray obj);
  protected abstract String processString(String obj);
  protected abstract String processSQLResult(ResultImpl obj);

  protected abstract String singleObjectWrapper(StringBuilder builder);
  protected abstract String multipleObjectWrapper(StringBuilder builder);
  
  @Override
  String toString(){
    
    if(map.isEmpty()){
      return "";
    }
    
    StringBuilder builder = new StringBuilder();
    
    for(Map.Entry<String, Object> entry: map.entrySet()){
      Object obj = entry.getValue();
      if(obj instanceof JSONObject){
        builder.append(processJSONObject(obj));
      }
      //...
      
      
    }
    
    if(map.size() > 1){
       multipleObjectWrapper(builder);
    }else if(map.size() == 1){
      singleObjectWrapper(builder);
    }
    
    return builder.toString(); 
  }
}