code: public String getStatisticsString() {
      StringBuffer sb = new StringBuffer();
      String opCodeName; 
      for(Byte opCode = -1; opCode < 15; opCode++) {
        switch (opCode) {
          case -1:
            opCodeName = "OP_INVALID";
            break;
          case 0:
            opCodeName = "OP_ADD";
            break;
          case 1:
            opCodeName = "OP_RENAME";
            break;
          case 2:
            opCodeName = "OP_DELETE";
            break;
          case 3:
            opCodeName = "OP_MKDIR";
            break;
          case 4:
            opCodeName = "OP_SET_REPLICATION";
            break;
          case 5:
            opCodeName = "OP_DATANODE_ADD";
            break;
          case 6:
            opCodeName = "OP_DATANODE_REMOVE";
            break;
          case 7:
            opCodeName = "OP_SET_PERMISSIONS";
            break;
          case 8:
            opCodeName = "OP_SET_OWNER";
            break;
          case 9:
            opCodeName = "OP_CLOSE";
            break;
          case 10:
            opCodeName = "OP_SET_GETSTAMP";
            break;
          case 11:
            opCodeName = "OP_SET_NS_QUOTA";
            break;
          case 12:
            opCodeName = "OP_CLEAR_NS_QUOTA";
            break;
          case 13:
            opCodeName = "OP_TIMES";
            break;
          case 14:
            opCodeName = "OP_SET_QUOTA";
            break;
          case 16:
            opCodeName = "OP_CONCAT_DELETE";
            break;
          default:
            opCodeName = "UNSUPPORTED OP";
            break;
        }
        sb.append(String.format(
          "    %-30.30s (%3d): %d%n",
          opCodeName,
          opCode,
          opCodeCount.get(opCode)));
      }
      return sb.toString();
    }
docs: Get the statistics in string format, suitable for printing
  (Copied from FSEditLog.java)
  
  @return statistics in in string format, suitable for printing