code: public String[] query_class() throws DevFailed {
          Util.out4.println("In QueryClass command");
  
          final int nb_class = class_list.size();
          String[] ret = null;
  
          try {
              ret = new String[nb_class];
  
              for (int i = 0; i < nb_class; i++) {
                  ret[i] = ((DeviceClass) class_list.elementAt(i)).get_name();
              }
          } catch (final OutOfMemoryError ex) {
              Util.out3.println("Memory Allocation error in DServer.query_class  method");
              Except.throw_exception("API_MemoryAllocation", "Can't allocate memory in server",
                      "DServer.query_class");
          }
          return ret;
      }
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