*
   * <p>If the character does not need to be escaped, this method should return {@code null}, rather
   * than an array containing the character representation of the code point. This enables the
   * escaping algorithm to perform more efficiently.
   *
   * <p>If the implementation of this method cannot correctly handle a particular code point then it
   * should either throw an appropriate runtime exception or return a suitable replacement

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   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  public static void awaitClear(WeakReference<?> ref) {
    awaitDone(() -> ref.get() == null);
  }

  /**
   * Tries to perform a "full" garbage collection cycle (including processing of weak references and
   * invocation of finalize methods) and waits for it to complete. Ensures that at least one weak

      assertTrue(queue.offer("blocksPutCallsUntilRemoved"));
      this.completed = new Completion(countdownInMillis);
      scheduleEnableWrites(this.queue, countdownInMillis);
    }

    /** Perform a {@code put} and assert that operation completed in the expected timeframe. */
    void putSuccessfully() {
      putUninterruptibly(queue, "");
      completed.assertCompletionExpected();

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