Reinventing wheels?

Although the sample code implemented tick synchronization between worker thread and robot thread, the use of token may not be necessary, since Java already had similar mechanism.

    worker = new Thread(() -> {
      try {
        while (true) {
          Thread.sleep(1000);
        }
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
      }
    });

call worker.interrupt() whenever you don't need it anymore, or just wait robocode to call that method for you.

It's more likely a sign of the state of Java (or the author's knowledge of it) at the time the page was drafted. It looks like the original is over 10 years old.

Besides Toad, do any bots actually make use of multithreading? I've always felt the community considered it to be a "dirty" tactic.

I'd be in favour of disabling multi-threading in the rumble, or somehow only allowing a single thread to run at the same time. Otherwise there could be some very dirty tactics like starving the opponent of CPU or memory bandwidth during their turns, which is against the spirit of trying to keep the bots' processing isolated except through the robocode engine.