code: @Override
      public void end(final boolean now) {
          if (now) {
              this.state.set(SHUTDOWN_IMMEDIATE);
              final Thread workerThread = this.threadRef.get();
              if (workerThread != null) {
                  workerThread.interrupt();
              }
          } else {
              this.state.set(SHUTDOWN);
          }
          togglePause(false); // Release any threads waiting in checkPaused()
      }
docs: Shutdown this Worker.<br>
  <b>The worker cannot be started again; create a new worker in this case.</b>
  
  @param now if true, an effort will be made to stop any job in progress