code: @Override
      public boolean cancel(boolean mayInterruptIfRunning) {
          boolean success = true;
          for (Future<FUTURE_TYPE> future : futureList) {
              success &= future.cancel(true);
          }
          return success;
      }
docs: Cancels all internal futures.
  
  @param mayInterruptIfRunning defines if waiting threads should be interrupted.
  
  @return true if all subfutures are successfully canceled.