* unsafely published. (The Entry object might even be newly created by each iterator.next()
     * call, so we can't assume that writes to the Entry have been safely published by some other
     * synchronization actions.)
     *
     * All that said: I haven't actually managed to make this particular test produce a TSAN error
     * for the field accesses in MapIteratorCache. This test *has* found other TSAN errors,

     * unsafely published. (The Entry object might even be newly created by each iterator.next()
     * call, so we can't assume that writes to the Entry have been safely published by some other
     * synchronization actions.)
     *
     * All that said: I haven't actually managed to make this particular test produce a TSAN error
     * for the field accesses in MapIteratorCache. This test *has* found other TSAN errors,

        // Note: This code path is horribly slow and typically allocates 4 new
        // char[] each time it is invoked. However this avoids any
        // synchronization issues and makes the escaper thread safe.
        char[] surrogateChars = new char[2];
        Character.toChars(cp, surrogateChars, 0);
        char[] hiChars = escaper.escape(surrogateChars[0]);

   * at a time, but since read operations and cache loading computations can proceed concurrently,
   * this still yields higher concurrency than full synchronization.
   *
   * <p>Defaults to 4. <b>Note:</b>The default may change in the future. If you care about this
   * value, you should always choose it explicitly.
   *

   * one input completes with result X and another later with result Y, for Y to come before X in
   * the output future list. (Such races are impossible to solve without global synchronization of
   * all future completions. And they should have little practical impact.)
   *
   * <p>Cancelling a delegate future propagates to input futures once all the delegates complete,

   * at a time, but since read operations and cache loading computations can proceed concurrently,
   * this still yields higher concurrency than full synchronization.
   *
   * <p>Defaults to 4. <b>Note:</b>The default may change in the future. If you care about this
   * value, you should always choose it explicitly.
   *

      }
    }

    private static class RunnableExecutorPair {
      final Runnable runnable;
      final Executor executor;
      // Volatile because this is written on one thread and read on another with no synchronization.
      @Nullable volatile RunnableExecutorPair next;

      RunnableExecutorPair(@Nullable Runnable runnable, @Nullable Executor executor) {
        this.runnable = runnable;
        this.executor = executor;