code: public void init() {
          if (executorService == null) {
              int numThreads = Math.min(Math.max(Runtime.getRuntime().availableProcessors(), 1), 4);
              executorService = Executors.newFixedThreadPool(numThreads);
              myOwnExecutorService = true;
          } else {
              myOwnExecutorService = false;
          }
      }
docs: Initializing method.